II 111 ' HI iimmmiiiiimimiui ill !l ! 1 II ' i li III llilr IMlHMllllilflllilllll Iflilfllffl ±^s\ HENRY C. STETSON GEOLOGICAL LIBRARY WOODS HOLE, MASSACHUSETTS A'Tjy '^ F GE#LOGY AND PALAEONTOLOGY IN THE UNIVERSITY OF MUNICH LIB Rary l-.'GC U01 ' ~ ■ MASS. TRANSLATED AND EDITED BY 'JHAELES E. EASTMAN, Ph.D. 0. /. IN CHARGE OF VERTEBRATE PALAEONTOLOGY IN THE MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD COLLEGE, CAMBRIDGE. MASS. ENGLISH EDITION REVISED AND ENLARGED BY THE AUTHOR AND EDITOR IN COLLABORATION WITH THE FOLLOWING SPECIALISTS : FISHES, A. S. WOODWARD | AMPHIBIA, E. C. CASE ; REPTILIA, J. B. HATCHER. H. F. OSBORN, S. W. WILLISTON ; AYES, F. A. LUCAS VOL. II. WITH 373 WOODCUTS ILonoon MACMILLAN AND CO., Limited NEW YORK: THE .MACMILLAN COMPANY 1902 EDITOR'S PREFACE The present volume continues the translation of Professor Von Zittel's Grundzilge der Palaeontologie through the Vertebrates as far as the class Aves, and corresponds in scope, though not in extent, to the third volume of the well-known Handbuch by the same author. The final volume, when published, will be devoted exclusively to the Mammalia. The translation of the Vertebrates has been conducted on the same plan as the preceding volume, and,- like it, has been appreciably enlarged. Although nearly all portions have received the benefit of expert revision, and some are of composite authorship, yet on the whole the original text has been more closely adhered to than in the case of the Invertebrates. The classification, also, departs from that of the Grundzilge in only a few minor particulars. The chapters on Fishes and Amphibians are chiefly in the nature of a literal translation ; those on Reptiles and Birds are more modified, at least in certain parts. Dr. Arthur Smith Woodward, of the British Museum, is to be credited with the entire translation and revision of the class Pisces, on which group he is acknowledged to be the most eminent living authority. He has been careful, however, to subordinate his views on various taxonomic points to those of the Author. In the same way Dr. E. C. Case, of the State Normal School at Milwaukee, Wisconsin, performed the principal labour of translating and revising the chapter on Amphibia, and assisted in the task of rendering the text on Pieptilia into English. Owing to the untimely loss of the late Dr. George Baur, of Chicago University, the text for the various orders of Pieptilia failed to receive the benefit of his collaboration. It is also to be deplored that the arrangements made with Professor 0. C. Marsh for the revision of the Dinosauria were cut short by the final passing in 1898 of this distinguished patron of Palaeontology. VI TEXT -BOOK OF PALAEONTOLOGY Grateful acknowledgments are due to Professor H. F. Osborn and Dr. ( ). P. Hay. <»f the American Museum of Natural History in New York, and to Mi. .1. B. 11 LTOHER, of the Carnegie Museum at Pittsburgh, for valuable notes and suggestions "ii the group of Reptiles, especially the order Dinosauria ; and to Professor S. W. WlLLISTON, of the State University of Kansas, for his revision of the Reptilian orders Squamata and Pterosauria, with notes on the Plesiosauria and Chelonia. To Mr. Frederic A. Lucas, of the United States National Museum at Washington, was confided the task of arranging the text for the class Aves in its present shape, which involved the rewriting of the entire systematic and most of the general or introductory part. The balance of the present volume, in so far as it departs from the original text, owes its condition conjointly to the work of the Author and Editor. In spite of the imperfections inevitable to a treatise produced in this manner, the hope is expressed that the subject-matter will be found more nearly up to date, and on the whole better adapted to the needs of English- speaking students than would have been the case had the Editor contented himself with bringing out a strictly literal translation. He would likewise speak a word of gratitude for the many favours and indulgences he has received at the hands of his friend and master, the Author. CHARLES R. EASTMAN. II v.rvard University, Jvhi 1902. CONTENTS CLASS I. PISCES . Sub-Class 1. Selachii Order 1. Pleuropterygii 2. acanthodii 3. ichthyotomi 1. Plagiostomi 5. holocephali 11 11 11 Sub-Class 2. Ostracodermi Ordek 1. Hetero.stracj 2. axaspida 3. aspidocephali 4. Antiarcha 11 5) 11 Sub- Class 3. Arthrodira Sub-Class 4. Dipnoi Order 1. Ctenodipterini „ 2. SlRENOIDEI Sub-Class 5. Ganoidei . Order 1. Crossopterygii „ 2. Chondrostei 3. Heterocerci 4. Lepidostei 5. Amioidei >> ii ii Sub-Class 6. Teleostei . Order 1 . Physostomi „ 2. Physoclysti CLASS II. AMPHIBIA Order 1. Stegocephalia 2. Gymnophiona 3. Urodela 4. Anura . ii ii ii PAGE 2 17 19 20 22 25 44 50 50 53 54 56 58 61 61 64 65 69 73 75 79 89 92 93 101 114 117 135 135 137 \ 111 TEXT -BOOK OF PALAEONTOLOGY "> 11 CLASS III. REPTILIA Order 1. Rhynchocephalia •2. Squamata 3. Ichthyosauri a 4. Sauropterygia 5. Theromorpha 6. Chelonia 7. Crocodilia 8. DlNOSAURIA „ 9. Pterosauria CLASS IV. AVES . Sub-Class 1. Saururae . Order 1. Archaeornithes Sub Class 2. Ornithurae Super-Order 1. Odontolcae Super-Order 2. Odontormae Super-Order 3. Dromaeognathae Order 1. Struthiones 2. Apteryges 3. Crypturi )j Super-Order 4. Euomithes Order 1. Impennes 2. Cecomorphae 3. Grallae 4. Chenomorphae 5. Herodii 6. StegAnopodes 7. Opisthocomt 8. Gallinae 9. Columbae 10. Accipitres 1 1 . Psittaci 12. PlCARIAE I 3. Passeres )» ?i V) 11 11 •>1 11 INDKX Phylum VIII. VERTEBRATA Bilaterally symmetrical animals, with a cartilaginous or ossified vertebral axis, which is usually composed of a series of similar segments, the same supporting the central nervous system and dividing the trunk into a dorsal and a ventral portion. Never more than two pairs of limbs. The vertebral column develops from a rod-like cellular tissue of gelatinous consistency (chorda dorsalis), of which the outer (skeletogenous) layer gradually subdivides into a number of similar segments, which are originally cartilagin- ous but subsequently calcified by the deposition of phosphate of lime or are replaced by bone substance. At the anterior end of the vertebral column is the cranial capsule enclosing the brain, also the visceral skeleton. The appendicular skeleton is likewise preformed in cartilage, and among the higher Vertebrata usually develops completely into bone substance. Only some of the lowest Vertebrata exhibit a persistently cartilaginous internal skeleton. The calcification of the cartilage in the sharks and skates takes place in such a way that a homogeneous limey substance is deposited between the cartilage cells, while in ossification the original cartilage cells disappear, and by re- sorption of the intercellular substance there arise canals with blood vessels (Haversian canals) as well as small hollow spaces (lacunae, bone corpuscles) filled with bone cells (osteoblasts). The latter are connected with the Haversian canals by very fine tubules (primitivrbhrchen) radiating in all directions. In many fishes the lacunae (bone corpuscles) are wanting, so that the primitive tubules arise directly from the Haversian canals. The skeleton of the extremities consists of several articulated segments which exhibit an extraordinarily varied arrangement according to the function of the limbs. The nervous system consists of a central organ divided into brain and spinal chord, from which numerous nerves arise and extend throughout the whole of the body. The blood is first driven to the organs of respiration (gills or lungs) by means of a heart provided with one or two auricles, and after it has traversed the body in numerous veins it returns to the heart. The oesophagus, stomach, intestine, liver, kidneys, and spleen, as well as the organs of generation, lie in the ventral part of the body. The skin is often provided with hairs, spines, scales, feathers, or bony plates. As a rule only remains of the bony skeleton, teeth, or hard ossified parts of the skin are available to the palaeontologist for investigation ; but these can generally be determined with great certainty. The following five classes of Vertebrates are distinguished : — Pisces, VOL. II B VERTEBRATA PHYLUM VIII Amphibia, Beptilia, Aves, and Mammalia. Recently the numerous groups of Tunicata and Leptocardii have been placed with these as special classes and often regarded as the ancestors of the Vertebrates. As these have left no fossil remains in the rocks, the palaeontologist discovers no clue to the origin of the Vertebrata. Class 1. PISCES. Fishes. Cold-blooded animals living in water and usually breathing exclusively by gills. Limbs in the form of fins. Skin with scales or bony plates, rarely naked. Vertebral axis ending in a vertical caudal fin. Heart with a single ventricle and auricle. No amnion or allantois. To the skin structures of fishes belong the scales, dermal bones, spines, fin rays, and teeth. Scales. — Louis Agassiz distinguished four kinds of scales, to which in his system there correspond as many orders. 1. Placoid scales occur only among the Selachians. They are usually small rhombic plates, star- shaped, 1 e a f - s h a p e d, pointed, spade -shaped, or even conical structures which lie close together and form a rough mosaic A B A, Scale Recent. 5 '/j (I'riui/ndon) Magnified. Fig. 1. of Set/Ilium fa itU- ula. B, Scales of CarcJiarias ganged cus. Recent. Fig. -2. Large placoid scale of Raja antiqua, with spine. Pliocene. Nat. size. (shagreen). The placoid scales are often of variable form on different parts of the body, and sometimes (e.g. among the rays) single tubules are conspicuous by their large size and sculpture, and appear as thick plates externally roughened or provided with spines. Placoid scales (Figs. 1-3) have the structure of teeth and consist of a basal plate (of thick phosphate of lime) penetrated by vertical bundles of connective tissue fibres sunk in the skin, and a freely projecting upper part composed of dentine and penetrated by coarser and finer little canals. All the canals arise from a cavity (pulpa, p) filled with connec- tive tissue and tooth cells (odontoblasts, o), and sub- divided outwards into continually finer branches. Besides phosphate of lime the dentine comprises small quantities of fluoride and carbonate of lime. The core of dentine is covered by a thin, shining, very hard structureless outer layer, which corresponds histologically and chemically with the enamel of Sagittal section through a scale of Scymuus lichia. Recent. 60/j. B, Basal plate. D, Dentine. S, Enamel ; c, Cutis ; d, Horizontal dentine canals ; /, Bundles of connective tissue ; h, Large principal dentine canal extending upwards; o, odontoblasts; p, Pulp cavity (after O. Hertwig). CLASS I PISCES B teeth. Placoid scales often fall out and are replaced like teeth by successional tubercles. 2. Ganoid scales (Figs. 4-7) attain a larger size than placoid, and usually cover the whole trunk. They are of rhombic or rounded shape, and in the latter case overlap one another like roofing tiles. Those of rhombic form are usually arranged in regular rows, and are movably articulated by a tooth-like process of the upper margin which fits into a corre- sponding hollow on the inner .side of the adjoining scale. The exposed outer face is covered by an enamel laver (ganoine) ; it is usually thick and shining, sometimes dark- coloured, smooth, rugose, or ridged, and beneath it there is a basal plate consisting of bone substance and pierced by numerous canals. Among the Palaeozoic genera, indeed, the basal plate shows great complexity. The deeper layers include numerous lacunae Fig. 4. Scale of Cosmoptychius striata*, Ag. sp. Outer (^1) and inner (Ji) aspects. Lower Carboniferous. 3 /j. Fig. :>. Two scales of Poly- jitrriis bichir, Bonap. Recent. Inner aspect. Nat. size. Fig. 6. Vertical section of a scale of Lepidosteus. Recent. S, Enamel; d, Dentine tubules; h, Haversian canal. 300/j (after ( ). Hertwig). Fig. i. Vertical section of a scale of Glyptolepis, highly magnified. Devonian, a, i>, Layer of vasodentine with spindle-shaped bone lacunae ; c, Bony layer with Haversian canals ; d, Layer with fine, branching dentine tubules (cosinine) ; e, Enamel (after Pander). (bone corpuscles) and Haversian canals, while the upper layers as a rule are traversed only by fine dentine tubules. 3. Cycloid and ctenoid scales are exactly alike in general characters, being thin, elastic, and of rounded, elliptical, four-, five-, or six-sided shape. They consist of a homogeneous, transparent shining surface-layer of phosphate of lime, and of a base of connective tissue deficient in alkalies. The scales are VERTEBRATA PHYLUM VIII B developed in special folds of the cutis, and generally overlap one another like roofing tiles. Cycloid scales (Fig. 8, A-G) generally exhibit a rounded or oval form and a simple non - serrated hinder border. In ctenoid scales (Fig. 8, D, -E) there project from the hinder border small points and denticles, which are sometimes arranged in several series one behind the other, and may indeed cover a con- siderable part of the hinder surface and have the same structure as the superficial layer. From the so - called primitive field divergent lines radiate chiefly forwards and backwards, and sometimes also pass into reticulations ; these lines being merely fissure-like interruptions in the outer layer (Fig. 9). Between the upper parallel layers of the fibrous connective tissue of the base there are often intercalated calcareous bodies, which are most fused with each other into Fir;. S. Cycloid scales of A, Leiiciscus, B, Mormyrus, and C, Naucrates Ctenoid scales of D, Solea, and E, Holacanthus. Much magnified. small, round, concentrically marked numerous beneath the primitive field, sometimes a continuous layer, and here and there exhibit bone cells. Such scales are not essentially different from very thin ganoid scales. The large plates, shields, spines, etc., which partly cover the body and partly the head of many fishes (Artlirodira, Siluridae, Acipenseridae), consist either of uniform bone substance, or, like the ganoid scales, of layers of ostaine, dentine, and enamel. Large spines (Ichthyodorulites), (Fig. 10) generally occur on the front margin of the median, and more rarely of paired fins, or on the head of carti- laginous fishes (Selachii). They are usually implanted loosely in the muscles by an elongated base, only exceptionally (Chimaera) articulated with a lower piece. Like the scales and teeth of Placoid fishes they consist either entirely of dentine or of dentine and vasodentine. Ichthyodorulites often attain a remarkable size, and occur isolated in a fossil state, while the Palaeozoic examples are sometimes characterised by a rich sculpturing. The outer projecting parts of the fins are also to be regarded as dermal Fig. 9, External surface of a scale of Pleuronectes, to show the vacuities (as) between the raised concentric lines. Very much magnified (after Baudelot). CLASS I PISCES structures. They arise as folds of skin, which gradually become strengthened by numerous horny fibres (Selachii, Dipnoi). In most Ganoids and Tele- osteans these fibres are replaced by bony rays, which consist of two closely apposed halves. In the Acan- thopterygii (Fig. 11) each half consists of a single piece ; in the Malacopterygii the rays are subdivided by transverse sutures into numerous little pieces and often branch towards the end. Spiny and articulated rays frequently occur in one and the same fin, and in this case the spines are always in front. The rays of the unpaired fins are borne as a rule on flat cartila- ginous or bony supports with which they articulate (Fig. 11, C). These^ fin supports penetrate between the spinous processes of the vertebrae and are known as axonosts or (according to their position) as inter- neurals and interhaemals. In many Selachians (Pristiophorus, Raja) every gradation can be observed between the Placoid scales of the external skin and the teeth ; and as both exhibit essentially the same histological structure, while the teeth only assume a firm connection with the head bones in the higher fishes, the teeth must indeed be regarded as dermal structures. Among fishes all the cartilages or bones surround- ing the mouth and gill cavity may bear teeth. They originate in the calcification of skin papillae, con- sisting of a crown wmich freely projects, and of a root which is surrounded with or united with Their form and Fig. 11. A, B, Rays from the dorsal tin of an Acan- thopterygian. C, Fin support or inters pi n- ous bone. connective tissue the head bones, proportions are extraordinarily variable according to their functions. All gradations exist from the minute granular denticles of the perch to the long brush-like teeth of the sheat-fish, to the robust pre- hensile teeth of the pike and the powerful conical or laniary teeth of Dendrodus or Portheus. Among the sharks there often occur teeth shaped like an arrow-head, flattened on one side, with or without lateral denticles. To crush the food there are sometimes obtusely conical teeth, sometimes bean-shaped, hemispherical, or pavement-like teeth, and in certain Selachii the teeth are closely pressed together into a continuous mosaic. Peculiar plates of considerable size occur in Diodon, Fia. 10. Dorsal fin spine of Hybodus. Upper Lias ; Boll. Wiirtemberg. cutting dental Chimaera. The number of the teeth in fishes is also as varied While the Dipnoi, Chimaeroidei, and Gymnodonts possess Arthrodira, and as their shape, onlv four to a VERTEBEATA PHYLUM VIII six teeth in all, in many Sharks and Teleosteans these are numbered by hundreds. In the young of almost all fishes the teeth are fixed to the cartilaginous or bony support by fibrous connective tissue, and in sharks and in many bony fishes this arrangement persists throughout life, so that after long maceration the teeth can easily be stripped off their base. In bony fishes and many ganoids the roots of the teeth become fused with the bone, and a socket-like elevation usually grows round the teeth. Exceptionally, teeth are also im- planted in distinct sockets. The successional teeth are usually developed by the side of the functional teeth and continually push them out. With few exceptions the crown of the tooth consists of dentine, vaso- dentine, and enamel, the root of vasodentine or osteodentine. The enamel forms a very thin brilliant homogeneous superficial layer, as hard as glass, and Vertical section of a tooth of Lepi- dotus (Sphaerodus) gigas, Ag. Con- sisting Of dentine (D) and enamel (S). Upper Jurassic. Much magnified. Fig. 13. Vertical section of part of a tooth of a pike (Esox). Recent. D, Dentine. S, Enamel. VD, Vasodentine. W, Root of tooth. Much magnified (after Sternberg). Fig. 14. Vertical section of a tooth of Otodus. Eocene. D, Dentine. S, Enamel. VD, Vasodentine. Much magnified. is easily recognised in polarised light by its double refraction. Very fine unbranched tubules frequently pass from the dentine into the enamel. It is composed of phosphate of lime, with a little fluoride of lime, a little carbonate of lime, phosphate of magnesia, and a very small quantity of organic matter. The dentine or tooth substance contains no fluoride of lime but much more organic matter than the enamel, is less hard, and dissolves more slowly in acids. Typical dentine (Fig. 12, D) is traversed by very fine outwardly branching tubules, which radiate outwards from the pulp or its branches, and contain thread-like processes of the tooth cells (odontoblasts). The dentine is also very frequently traversed by large anastomosing canals (Haversian canals), in which blood-vessels penetrate, and the walls of which are covered with odontoblasts. Fine dentine tubules then radiate in a peripheral direction from these large canals. This vascular modification of tooth substance is known as vasodentine (Figs. 13, 14, VD). class i PISCES 7 The root of the teeth of fishes is distinguished from the crown by the absence of an enamel layer. It consists either entirely of vasodentine, or also exhibits bone cells with radiating primitive tubules (osteodentine). The internal skeleton of fishes shows that in the different orders of this class there persist until adult life almost all the stages of development which are only temporary among the higher Vertebrates. The whole process of the gradual segmentation, chondrification, and ossification of the vertebral column and of the rest of the skeleton is quite clear in the different groups of fishes, and the fossil forms from the Palaeozoic and Mesozoic deposits furnish the most important information in this -respect. Vert thrui Column. — The first trace of the internal skeleton in all Vertebrata is confined to an elastic rod-like structure (chorda dorsalis) extending longi- tudinally on the dorsal side of the body, consisting of oil-bearing cells, and enveloped in a laminated sheath. Upon the chorda dorsalis lies the spinal chord ; below it, the ventral cavity of the body. The vertebral column persists throughout life in this primitive stage only in Amphioxus. The notochord, indeed, still remains unsegmented in the Cyclostomes, but the spinal chord is already protected by arch-shaped bars of cartilage developed in the sheath of the notochord (neural arches) ; and at the front end there is developed a cartilaginous capsule for the reception of the brain. In all typical fishes the notochord is divided into ring-shaped segments (vertebrae), and is partly or completely cartilaginous or bony. The chondri- fication or ossification alwavs arises in the outer skeletogenous laver of the notochordal sheath, and begins with the upper and lower arches. A complete vertebra consists of a vertebral body (centrum) surrounding the notochord, two upper half-arches surrounding the neural canal (neuro- pophyses), and two lower half-arches (hemapophyses). The upper arches are united with a dorsal spinous process (processus spinosus, spina dorsalis, or neural spine), while the lower arches either unite in the caudal region into a ventral spinous process (spina ventralis), or remain as lower transverse processes na — £3Sl SKsE'""" (parapophyses). p^JJoJv In many fishes provided with a cartilaginous vertebral column (Selachians and Acipenseroids), there -iisSlplli! are interposed between the upper and lower arches J| cartilaginous intercalary pieces (intercalaria) which ha W^gg^^^ sometimes exceed the arches in size (Fig. 15, i). The vertebral centra or vertebral bodies in cartila- Three cnni{ . d{ ver tebrae of Hnous fishes usually surround a persistent remnant Cmtrophorus in side view, ha, 1/ jl IfiHiii'il 'i rentes * / lntt'ivHiflrv of the notochord, which pierces the whole of the cartilages; na, Neural arches; vertebral column and partly fills the intervertebral a' a sse)? r spaces. The cartilaginous, calcified, or bony anterior and posterior faces of the vertebral bodies are deeply hollowed like double cones (amphicoelous), and thus give the centrum an hour-glass shape. In the Selachii there is usually a partial calcification, in the Ganoidei and Teleostei an ossification of the primitive cartilaginous centrum. While, however,, the bony fishes generally exhibit complete ossification of the whole vertebra with all its processes, the ganoids of the Palaeozoic and Mesozoic deposits display every possible stage in the process of VERTEBRATA PHYLUM VIII ossification. In completely ossified vertebrae the anterior and posterior edges of the amphicoelous centra are in close contact and also bound together by ligaments : the notochord persists only in the intervertebral spaces, and does not form a continuous thread. The arches are firmly fused with the centrum, and on the anterior margin of the upper arches there usually projects a short process (zygapophysis), which overlaps a similar posterior process of the centrum on each side, and thus strengthens the union of contiguous vertebrae (Fig. 17). In the hinder or caudal region the lower arches form a ventral spinous process Fig. 16. Vertebrae from the abdominal region of the Sturgeon (I *g- 1') j in the anterior Or abdominal (Acipenser), in side view (A) and I in vertical transverse re on n the lower arches proiect as short section (B). Cartilage dotted, bone white, ch, Is oto- o J chord ;/, Nerve foramina ; ha, Haemal arches ; i, Inter- calary pieces; m, Neural canal; n, Neural arches; p, Transverse processes (parapophyses) ; r, Ribs ; s, Sheath of notochord ; sp, Neural spines (after R. Hertwig). C parapophyses, and serve as supports for the movable ribs. True transverse processes (diapophyses, processus trans- versi), to which the ribs are attached in the higher Vertebrata, and which arise from the upper arches, occur only exceptionally (Polypterus, Pleuronectes) besides the parapophyses. In the Cyclostomi and Chimaeras ribs are entirely absent ; in the Selachii and cartilaginous ganoids they are usually feebly developed or rudimentary. The ribs of the two sides are never united with each other at the ventral border either directly or through the intervention of a sternum. The inter- muscular bones, which arise in the membrane between the muscle plates, must not be confounded with ribs ; they are delicate bony filaments, often forked at one end, which are disposed between the muscles, and rest on the vertebral centra, arches, or ribs. The number of the vertebrae in fishes varies most remarkably in the different groups. In certain bony fishes (Ostracion) only 15 are to be counted, while in others there are 70 to 80, in the eel about 200, in many sharks from 350 to 400. The hinder end of the vertebral column in the embryonic stage of all fishes is diphycercal or heterocercal. In the first condition the vertebral column Fig. 17. Caudal vertebrae of the Carp. A, Vertical longitudinal section of three vertebrae. B, Detached vertebra, chiefly in side view. C, Last abdominal and first caudal vertebra, c, Centrum ; eft, Notochord ; ha, Haemal arches ; n, Neural arches ; sp.d, Neural spines ; za, Zygapophyses (after R. Hertwig). CLASS I PISCES extends in a straight line to the end of the trunk, and is symmetrically fringed above and below with the caudal fin. The Cyclostomi: Dipnoi and many Crossopterygii (Fig. 18) remain in this embryonic stage throughout life In the heterocercal fishes (sharks, rays, many ganoids) the end of the vertebral Fig. 18. Fig. 19. column is bent upwards, and completely passes into the upper lobe of the caudal fin, which is usually elongated, and exceeds the lower lobe in size (Fig. 19) Between the diphycercal and heterocercal types of tail there are many gradations. In the hetero-diphycercal tail the vertebral column is elongated in a gentle upward curve at its hinder end, and fringed above and below with Fig. 20. Internally heterocercal caudal tin of Amia Recent, ch, Cartilaginous hinder end of the ver- tebral column, with rudiment of notochord (after Kolliker). Externally homocercal (stegurous) caudal tin of the Salmon (Salmo salar). <<, b, c, Upper roofing bones of llic end of the notochord; ch, Projecting end of the notochord (after Kolliker). fin rays ; but the rays of the upper lobe are much less developed than those of the lower lobe. Sometimes also the external caudal fin consists of two similar lobes, while the vertebral column is bent upwards, and extends far into the upper lobe (Fig. 20). Such fins are externally homocercal, internally heterocercal. In the hemi-heterocercal tail the upper lobe of the externally symmetrical caudal fin is still partly or completely covered with scales. 10 VERTEBRATA PHYLUM VIII Iii all cycloid and ctenoid fishes the caudal fin is externally and internally homocercal (Fig. 21). The vertebral column terminates in front of the fin with a vertebra bearing a broad, vertical, fan-shaped plate (hypural), which is formed by the fusion of several fin supports and haemapophyses. This terminal plate generally encloses a short, upwardly directed remnant of the notochord or a bony style (urostyle). There is thus an internal heterocercy as the basis of the homocercal tail. Nearly all Palaeozoic fishes have a diphycercal or heterocercal tail ■ hemi- heterocercal forms begin with Acentrophorus in the Upper Permian, and are common in the Triassic and Jurassic. The Cretaceous, Tertiary, and Recent bony fishes, when adult, exhibit a homocercal tail ; but in their immature condition there is always a diphycercal or heterocercal stage. Skull, — The head forms the anterior end of the vertebral axis, and its skeleton exhibits a greater complexity in fishes than in the higher Vertebrates. Except Kr Po Fig. 22. Skull and branchial apparatus of Squatina vulgaris, Risso. Recent. BR, Rays of the hyoid arch ; CBr, Cerato- branchial ; Co, Copula of the hyoid arch ; Co', Hindermost copula of the branchial arches ; EBr, Epibranchial ; Etli, Ethmoidal region ; Hi/, Hyoid arch ; HBr, Hyobranchial ; HyM, Hyomandibular ; L, U, L", Anterior (pre- niaxillary), posterior (maxillary), and inferior (preniandibular) labial cartilages ; Md, Lower jaw or mandible ; Occ, Occipital region ; Po, Postorbital process ; PQ, Palatoquadrate. III-VII, Branchial arches (after Gegenbaur). in Amphioxus, the brain is enclosed in a cartilaginous or bony capsule, the skull or cranium, which also contains the organs of hearing, sight, and smell. With the skull are connected a large number of paired cartilaginous or bony pieces, which together form the so-called visceral skeleton. The embryonic primordial cranium of all Vertebrates is cartilaginous, and is developed like the vertebral column round the notochord, which always extends far into the base of the skull. Among the Selachii (Fig. 22) the whole cranial skeleton is cartilaginous, and only exceptionally hardened by the deposition of phosphate of lime (Ichthyotomi). The long cranial capsule does not exhibit any sutures, and comprises in its anterior part (ethmoidal region) the olfactory nerves, in the middle (orbital region) the optic nerves and eyes, in the hinder part the organs of hearing and the hemispheres of the cerebrum and cerebellum. The visceral skeleton consists of a number of variously shaped cartilaginous arches, of which the foremost (palatoquadrate) surrounds the cleft of the mouth, and is characterised by its relatively large size. The two movable branches of CLASS I PISCES 11 the lower jaw are articulated with the palate-quadrate. Two small labial cartilages, sometimes termed maxilla and premaxilla, occur on each side in front of and below the palatoquadrate. The latter element is connected with the skull in the ethmoidal region by ligament, and in the hinder portion by the second visceral arch, of which the upper portion (hyomandibular) is in contact with the auditory region of the skull, while the lower portion forms the hyoid arch. The palatoquadrate and mandible are provided with teeth. Behind the hyoid arch there follow five (rarely seven) other visceral arches, which serve for the support of the respiratory organs, are composed of several pieces, and united ventrally by median intercalary pieces (copulae). Both the gill arches and the hyoid bear cartilaginous gill rays. In the Holocephali the palatoquadrate and hyomandibular fuse together and w T ith the cranial capsule. The mandible thus becomes autostylic, i.e. articulates directly with the cranium. In the cartilaginous ganoids (Acipenser, Spatularia), bony elements begin to take part in the formation of the head. The cranial capsule, indeed, remains for the most part cartilaginous ; but externally there are a number of bony plates, which cover the cranium on the top and sides, and there is also developed below the base of the skull a long, delicate, dermal bone (parasphenoid), which extends forwards to the ethmoidal region and backwards even beyond the occiput. The palatoquadrate, hyomandibular, and mandible are also covered with bone ; and the fold of skin covering the gill clefts is likewise ossified as a single gill cover (operculum). The palatoquadrate and hyomandibular form the freely movable (hyostylic) supports of the mandible. The Dipnoi resemble the cartilaginous ganoids, except that in them the palatoquadrate and hyomandibular are fused with the cranium (autostylic). In the scaly ganoids and bony fishes a more or less complete ossification of the cranial capsule and visceral skeleton occurs. The ossifica- tion begins first, as in the carti- laginous ganoids, w T ith dermal bones, and then the substitution of bony substance for cartilage follows. The distinction between dermal bones and ossified carti- lage (cartilage bones) can, how- ever, onlv be made bv determin- ing their mode of development. In the cranium proper (Fig. 23) three regions are distin- guishable — the occipital portion, the auditory, and the orbito- ethmoidal regions. The hinder Fig. --'3. Cranium of the Carp (I carpio, Linn.). AIS, Ali- sphenoM ; />'", Basioccipital ; BSph, Basisphenoid : / . Ep itic ; Kth. Ethmoid ; Exo, Exoccipital ; Ir, Frontal ; io, [nterorbital ; Opu, Opisthotic ; OSph, Orbitosphenoid ; Prf, Prefrontal : 1 Prootie ; Ft/, Postfrontal ; SO, Supraoccipital ; Sq, Squamosal ; Vo, Vomer (after Et. < >wen). most or occipital region consists of four cartilage bones: — (1) The lower occipital bone (occipitale basilare, basioccipital), which usually contains a persistent remnant of the notochord, and is in contact with the vertebral column with its deeply hollowed hinder end; (2, 3) a right and left lateral occipital (occipitalia lateralia, exoccipitals), which bound the greater part of the foramen magnum ; and (4) an upper occipital (occipitale superius, supra- 12 VERTEBRATA PHYLUM VIII occipital), which belongs to the cranial roof, often thrust between the parietal bones, and provided with a vertical median crest. The auditory capsules are surrounded laterally by several pairs of bones often completely covered by the facial and other membrane bones. Among them are distinguished immediately in front of the exoccipitals the opisthotic (OpO), the epiotic (EpO), adjoining the latter in its hinder upper part, and the prootic (PrO), which is usually pierced by the trigeminal nerve. With these bones, which form the auditory capsule proper, there is connected a bony plate on each side above and in front of the opisthotic, which originates partly from membrane, partly from cartilage, and is named the squamosal (Sq) or pterotic (W. K. Parker) ; the mandibular suspensorium (hyoman- dibular) articulates with its lower face. The lateral investment of the middle orbital region of the skull, which sometimes remains cartilaginous or membranous, and is sometimes more or less completely ossified, consists externally of facial bones. Two pairs of bones can be distinguished here, posteriorly the alisphenoid placed just in front of the prootic, and anteriorly the orbitosphenoid ; both pairs, but especially the orbitosphenoids, often fuse together completely in the middle line. The base of the skull A Ec P"- s.o is formed by a large dermal bone, the long, sword- shaped parasphenoid, which abuts behind on the basioccipital, in front on the vomer. The roof of the two hinder regions of the skull only rarely arises in carti- lage ; it usually consists of membrane bones, which are intimately connected with the cartilage ele- ments. There are thus intercalated between the supraoccipital and the squamosals two parietal bones, and these are followed in front by the two frontal bones, which often fuse together into a large simple plate. By the side of the latter and / Ell, Fig. 24. Cranial skeleton of the Salmon. The persistent cartilage of the cranium dotted ; the bones developed from cartilage lettered in italics, the membrane bones in Roman type. A, Eye; Ang, Angular; Art, Articular; Br.R, Branchiostegal rays; C.lly, Ceratohyal; D, Dentary ; E.Hy, Epihyal; Ep.O, Epiotic; Eth, Ethmoid; Fr, Frontal; G.Hy, Glosso- h yal ; H.Hy, Hypohyal ; HM, Hyomandibular ; IOp, Interoperculum ; Ju, Jugal ; L, Lachrymal; M.l't, Mctapterygoid ; Ms. Ft, Mesopterygoid ; Mx, Maxilla; Na, Nasal; Op, Operculum; Pa, Parietal; Pmx, Premaxilla ; POp Preoperculum ; Pt, Palatine] PtM Pterotic (mth squamosal) ; Qu, ' m f ront f the squamosal Quadrate; S.O, Supraoccipital; Sb. Or, Suborbitals; SOp, Suboperculum ; 1 «■ i S< )r, Supraorbital ; Sy, Symplectie (after Parker). there OCCUrS the postirontal (sphenotic, W. K. Parker), which belongs to the membrane series in the Ganoids, but is a cartilage bone in the Teleosteans. There is also occasionally a small supraorbital above the eyes. The anterior ethmoidal region possesses as its base the vomer (/""<>) or ploughshare bone, which also forms the anterior part of the roof of the hard CLASS I PISCES 13 palate. From the vomer on either side there slopes upwards and outwards a prefrontal bone (ethmoidale laterale, W. K. Parker), which is connected above with the frontal and with the ethmoid (Eth\ which surrounds the nasal capsule above, in front, and partly at the side. One or more small ossifica- tions above each nasal opening, which are sometimes fixed to the outer face of the ethmoid, are termed nasal bones or nasalia (Na). To the visceral skeleton (Figs. 24, 25) belong the jaw apparatus, the facial bones, and the gill arches. The hyomandibular is in close connection with the hinder part of the palatoquadrate. Thus arises the so - called suspensorium, which, as support of the mandible, is movably connected by ligaments with the skull. The quadrate articulates below with the mandible, and is firmly fixed above with the symplectic which occurs at the lower end of the hyomandibular. From the quadrate there extends forwards the angularly bent ectopterygoid, upwards the metapterygoid, and again forwards the meso- pterygoid, of which the anterior end is connected with the palatine. The latter is fixed by cartilaginous liga- ments at its anterior border to the vomer and the ethmoidal region. In front of the palatine on each side there occur two pairs of rather large bones, which are usually pro- vided with teeth. The anterior of these, the premaxilla or intermaxilla, meets its fellow of the opposite side in a symphysis in front of the ethmoid region. The hinder bone, or maxilla, is sometimes connected with the quad- rate through the intervention of a slender jugal or supramaxillary. The lower jaw (mandibula) consists of the articular, a postero - inferior which often remains carti- GHy Llli! angular Fig. 2-3. Kinht half nf the hyoid and branchial arches of tin- laginoUS, and the large principal piece Pexch (Perm fiuviatilis, Linn.). BrB, Branchiostegal or dentarv fdpntalf^ which nsnallr rays ; Co, Copulae of branchial arches ; .Effy, Epihyal ; oi ueniaiy ^ucnuuc;, w men usually GHy ^ Glossohyal . HHy ^ H ypohjal ; IHy, Interhyal ; bears teeth. On the inner side there Phs > upper pharyngeal bones; UHy, Urohyai; n, , , " , -I • 1 Hyoid arch ; III-VI. Branchial arches (after Cuvier). is also a membrane bone, the splenial (or operculare), which* not unfrequently bears teeth, and sometimes (as in the Crossopterygii) consists of two or more bony pieces. Several opercular bones arising from a fold of skin attain a remarkably great development both in the Ganoidei and Teleostei. The foremost, or preoperculum, is usually a rather long, slender, slightly arched, bony plate, which is connected above with the hyomandibular, below with the quadrate. Behind this there is an operculum, usually of relatively large size, bounded below by a suboperculum, often also by an interoperculum, which is connected with the hinder end of the mandible. A variable number of small dermal bones or suborbitals (suborbitalia) form the arched posterior and inferior margin of the orbit. The supraorbital (SOr) above and the lachrymal (L) in front are small dermal bones, which are in close connection with the cranium, but are only rarely developed. 14 VERTEBKATA phylum viii The gill apparatus (Fig. 25) of the Ganoidei and Teleostei does not differ essentially from that of the Selachii, except that the gill rays supported by the hyomandibular in the latter are replaced here by opercular plates, while behind the hyoid there are never more than five (rarely four) bony arches, and the branchiostegal rays of the hyoid arch become robust bony pieces or plates. The hyoid is subdivided into an upper epihyal, a middle ceratohyal, and a small hypohyal (basihyal) consisting of two pieces ; the median connecting piece (copula) is extended more or less forwards into the tongue as a glossohyal, and is sometimes covered with teeth, sometimes toothless ; a second segment of bone belonging to the copula, directed backwards, is named urohyal. The gill branches (branchialia) also consist each of three pieces (epi-, cerato-, and hypo-branchiale), connected in the median line with copulae, and beset throughout their entire length with delicate cartilaginous rays, some- times also on their inner side with tooth-like prominences or spines. With the epibranchials are also connected the short upper pharyngeal bones, which often bear teeth. The last branchial arch is usually more or less modified, and forms the lower pharyngeal bones. The limbs of fishes comprise not only the paired, but also the unpaired fins, since both function as organs of locomotion. While, however, the latter are exclusively dermal structures, the paired fins belong at least in part to the internal skeleton, and correspond with the extremities of the higher Vertebrata, the pectoral fins with the anterior, the pelvic or ventral fins with the posterior limbs. Both the pectoral and pelvic fins are connected with originally cartilaginous arches (pectoral and pelvic girdles), which may become ossified and covered with bony plates in variable number. They are entirely absent only in Amphioxus and the Cyclostomi. Except in the Selachii, the pectoral girdle is usually fixed to the supraoccipital or squamosal bone. In the Selachii (Fig. 28, A) it forms a simple arch of cartilage, ventrally closed, situated behind the gills, its upper ends either terminating freely (sharks) or connected with the vertebral column (rays) ; it is bent upwards at the insertion for the fins, and pierced by nerve foramina. In many Ganoids (Chondrostei, Heterocerci, Crossopterygii) the primary cartilaginous pectoral girdle, divided into two pieces by a ventral suture, is covered on each side by three membrane bones, of which the median and largest is termed clavicula, the lower one infra- clavicula, the upper one supraclavicula. The latter is sometimes divided into two pieces, of which the upper is named post-temporal. In the other Ganoids and the Teleosteans the primary pectoral girdle is entirely replaced by ossifica- tion. The girdle is here formed of two bones united by jagged suture on the postero-internal face of the very large clavicle, the hinder element homologous with the scapula, the antero-anterior element with the coracoid. In several families there is also a third, slender, arched bar {Spangenstiick or precoracoid), extending downwards and inwards to the lower end of the clavicle. The clavicle is always the principal bone of the pectoral girdle in the Teleostei, and its size and form vary remarkably. A supraclavicle and a post-temporal (Pt) rest on its upper end ; while an ordinarily slender acces- sory dermal bone, the post-clavicle, overlaps it behind. The pectoral fins themselves can only be homologised in part and with difficulty with the anterior extremities of the higher Vertebrata. If we accept, with Gegenbaur, the biserial fin of Ceratodas (Fig. 26) as the basal CLASS I PISCES L5 Pig. 26. Pectoral tin of Ceratodus forsteri, Krefft. Recenl ; Queensland, a, Basal cartilage; b, Fin; C, Pectoral arch. type most closely approaching the primitive fin (archipterygiuni), we observe, fixed to the mainly cartilaginous pectoral girdle, two large pieces of cartilage, followed by a long row of smaller cylindrical or square segments, from which cartilaginous rays diverge on each side. The extinct Selachian genus Pleur acanthus also possessed a central axis in the pectoral fin ; but in all the other Selachii the cartilaginous rays are in one series. In the latter there are three large adjacent basal cartilages, the promeso-, and metapterygium, connected with the pectoral girdle, and each bears several rays consisting of pieces of cartilage (Fig. 27). The metapterygium is always the stoutest ; the two others are often much reduced or may even be completely absent. The dermal part of the fin is itself always supported by numerous horny filaments in pairs. In the Ganoidei, and still more in the Teleostei, the segments radiating from the basal pieces are extremely degenerate. Pohjpterus (Fig. 28, B) retains the three basal pieces of the Selachii, but in most of the other Ganoids the metapterygium forms almost the sole support for the fin — the meso- and propterygium are atrophied. Two or three rays, however, enter the same row as the basal pieces and are connected with the shoulder girdle. In the same manner the base of the pectoral fin in the Teleostei (Fig. 28, C) consists almost invariably of four to five similar, flattened, bony pieces, with which a varying number of short little cartilages are connected. In propor- tion as the peripheral parts of the primary fin skeleton degenerate, ossified fin rays are developed as secondary structures on each side of the dermal fin expansion. The so-called pelvic girdle of the hinder extremity is considerably simpler than the pectoral girdle. Among the Selachii it appears as a paired or un- scl Fia. -J7. Pectoral tin of Squa- tina vulgaris, Risso. With outer dermal rays removed, ms, Meso- pt irygium ; rat, Meta- pterygium ; p, Pro- pterygium ; /', Radials. Fig. 28. Pectoral arch and tin of A, Heptanchus (Selachii). /;, Polypterus (Ganoidei). C, Salmo (Teleostei). d, clavicle ; co, Coracoid ; fs, Outer dermal tin rays (exoskeletal) ; ms, Mesopterygium ; ml, Metapterygium ; p, Propterygium ; pel, Postclavicle ; pt, Post-temporaf ; /■, Basal rays (endoskeletal) ; sc, Scapula : scl, Supraclavicle. paired rod pierced by nerve foramina, either lying in the longitudinal axis of the body or forming an arch, convex in front, concave behind. To this girdle are attached the two basal pieces (pro- and metapterygium) of the pelvic fin, which bear a single series of cartilaginous rays on their outer side. Among 16 VERTEBRATA phylum v hi the Ganoids Polyptei us alone retains two small pieces of cartilage as remnants of a pelvic girdle ; in all other ganoids, as well as in the Teleostei, the pelvic girdle is completely wanting, but the metapterygium of each side attains a remarkable size, and forms the whole fin support, sometimes as a simple elongated bone, sometimes as a plate forking into two pieces. In the Ganoidei the rays belonging to the fin skeleton are occasionally bony ; in the Teleostei, on the other hand, they are usually cartilaginous, much reduced, sometimes indeed completely absent. The membrane of the fin itself comprises numer- ous articulated bony rays. In the Dipnoi the pelvic girdle exhibits a peculiar development. It consists of an unpaired, quadrangular plate of cartilage, which is produced forwards into a long process, and supports the cartilaginous axis of the biserial fin. While the pelvic fins of the Selachii, Ganoidei, and Dipnoi are always situated near the hinder end of the abdominal cavity, they are often displaced forwards in the Teleostei, becoming even connected with the pectoral girdle. Through this forward displacement of the pelvic fins there arise striking modifications in the general aspect of the bony fishes, which are of great importance as a means of classification. The fossil bones of fishes can generally be recognised with certainty by their external form. Their outer surface usually exhibits a characteristic aspect, on account of numerous small rugosities, open- ings of canals, and striatums ; while tubular bones with a medullary cavity are here entirely wanting. From the histological point of view, the bones of many fishes are noteworthy for the absence or very sparse develop- fig. 29. ment of bone cells. Ear bones (otoliths) of a -r< -i i 1 Tii /-n- nrw i Teieostean fish, outer (A), and dossil ear bones or otoliths {rig. 29) are also some- LTttdoff.' as S tS size° lig0cene ; tim es found with the hard dermal structures and the skeleton. These do not consist of phosphate, but of carbonate of lime, and exhibit great variety in their shape, the sculpturing of their surface, and the nature of their borders. Since the work of Aristotle, the classification of fishes has been based chiefly on the characters of the internal and external skeleton, on the nature and arrangement of the fins, and on the organs of respiration. Artedi, Bonaparte, Lacepede, Cuvier, and Valenciennes distinguished the cartilagin- ous fishes from those provided with a bony skeleton, and again subdivided both sections in different ways into several groups. In this classification no reference was made to fossil fishes, although sharks' teeth, for example, teeth of various bony fishes (the so-called bufonites, chelonites, toad-stones, and snakes' eyes), and also complete skeletons from different localities (e.g. Eisleben, Solenhofen, Oeningen, Monte Bolca, and Glarus) were already known in the eighteenth century and numbers of them had been described. The epoch-making work of L. Agassiz (1833-1844) afforded a complete survey of all the fossil fishes known at the time, and also established on scale characters a new subdivision of the fishes into four principal groups, namely, Placoidei, Ganoidei, Cycloidei, and Ctenoidei. Johannes Miiller united the two latter groups under the denomination of Teleostei (bony fishes), defined the ganoids more precisely, and subdivided the cartilaginous fishes into four sub- classes, namely, Leptocardii, Cydostomi, Selachii, and Dipnoi. The most important of the later changes in classification consist in the establishment SUB -CLASS I SELACHII 17 of the Leptocardii (Amphioxus) and Cyclostomi (lampreys and hag-fishes) as independent classes equivalent to that of the fishes, and in the closer union of the ganoids and bony fishes, which are frequently grouped under the common denomination of Teleostomi. The class of fishes in its restricted sense thus comprises the four still-existing sub-classes of Selachii, Dipnoi, Ganoidei, and Teleostei ; while to these must be added the extinct sub-classes of Ostracodermi (or Ostracophori) and Arthrodira, which are restricted to the Palaeozoic. No fossil remains of Leptocardii are known. It must also be remarked that there is no satisfactory evidence of extinct representatives of the Cyclostomi or Marsipobranchii. Certain annelid jaws from the Palaeozoic formations, known as Conodonts, were once erroneously supposed to be teeth of this class (see vol. i. p. 255). The problematical organism from the Old Red Sandstone of Achanarras, Caithness, named Palaeo- spondylus gunni 1 by Traquair (Fig. 30), is likewise very doubtfully placed here. The largest specimens of this form do not exceed 0'05 m. in length. The skull terminates in front in a ring of calcified cirri (d.c, l.c, v.c), which surround a large bilaterally symmetrical orifice {it). Behind the skull there extends backwards a pair of elongated cartilages (x), usually lying in the fossil parallel with the vertebral column. There are vertebral centra in the form of broad rings • in the these bear short and stout neural Fig. 30. abdominal region Palaeospondylus gunni, Tra- quair. Lower Old Red Sand- stone ; Caithness, a, Separate small lobe ; b, Anterior depres- sion or fenestra ; c, Posterior de- pression or fenestra ; d.c, Dorsal spines, out no rios ; in tne caudal region tne neural cirri ; z.c, Lateral cirri ; %,Suj- 1 ' J o posed narial opening ; p.a, rara- and haemal spines are very slender, while the former cnordai portion of skull; t.p, t ,-, -11 i t •• .i t i , • Trabecule - palatine portion of are longer than the latter and distinctly dichotomise skull; v.c, Ventral cirri ; *,Pro- at the distal end. There is no undoubted evidence of §^STnS£S iBitilBi * te8; paired limbs. but no ribs ; in the caudal region the neural Sub-Class 1. SELACHII. Cuvier. (Elasmobranchii, Bona]).; Chondropterygii, Cunther; Placoidei, Ag.) Endoskeleton cartilaginous; exoskeleton, when present, structurally identical with the teeth (placoid scales). Usually five {rarely six or seven) pairs of branchial arches, the clefts exposed or covered only hy a flap of skin, without operculum. In the living forms — optic nerves not decussating but forming a chiasma; bulbus arteriosus of the heart with two, three or more series of valves; air-bladder absent ; ■intestine with a spiral valve ; ovaries with feiu large ova. The unsegmented cartilaginous cranium of the Selachii is more or less imperfectly hardened with polygonal granules of phosphate of lime ; but the vertebrae are very variously calcified, can thus be readily preserved in a fossil state, and, according to Hasse, display features of special importance for the 1 Dean, B., The Devonian "Lamprey" Palaeospondylus gunni, Traquair (.Mem. N.Y. Acad. Sci. vol. II. pt. 1), 1900. Bibliography. — Traquair, A'. //.. A still further contribution to our knowledge of Palaeospondylus (Proc. Ptoy. Phys. Soc. Edinb. vol. XII.), 1894. VOL. II C 18 PISCES CLASS I purposes of classification. In the sharks and skates the pterygoquadrate cartilage of the upper jaw is movably suspended from the cranium, and the vertebral axis is often distinctly segmented ; in the Chimaeroids (Holocephali) the upper jaw is fused with the cranium and the mandible articulates directly with this, while the notochord remains unsegmented, so that the vertebrae are always indicated only by the arches. Among the sharks (Plagiostomi) the Notidanidae exhibit the most primitive vertebral axis (Fig. 31). Here regularly spaced thickenings of the notochordal sheath constrict the chord itself and form divisions pierced through the middle (Diplospondyli). The term Cyclospondyli is applied by Hasse to those vertebrae in which a calcified ring appears uniting the d cJu-S Fig. 31. ~ Longitudinal section of the anterior part of the vertebral column of Heptanchus. eh, Notochord ; d, Incipient calcified double -cone (basis of centrum) ; iv, Intervertebral space filled with notochord ; w, Constriction of notochordal sheath (after Kolliker). ,.eh Longitudinal section of the tectospon- dylic vertebral column of Squatina angelus, Linn, eh, Notochord : ?s, Beyr. ; Traquairia, Fritsch), (Figs. 37, 38). A more elongated fish with similarly remote dorsal fin, but the pelvic fins relatively small and advanced forwards, the pectorals larger, and intermediate spines absent. Teeth minute or absent ; circumorbital ring of four more or less sculptured plates. Pectoral fin spine supported by a hollow, mesially constricted element (Fig. 37, b), which abuts against the side of its proximal end ; a close series of short, fine dermal rays (r) some- times appearing below this in the fin-membrane. Scales smooth. Ranging throughout the Carboniferous in Scotland, the Coal Measures in England and North America, and the Lower Permian in France, Germany, Bohemia, and Siberia. A. bronni, Ag., the typical species, about 03 m. in length, from the Rothliegende of Rhenish Prussia (Lebach and Saarbriicken). A. gracilis, Beyr. (Fig. 38), from Klein Neundorf, Silesia, probably identical with the latter. A. wardi, Egert., from Coal Measures, Longton, Staffordshire. Cheir acanthus, Ag. Like Acanthodes, but dorsal fin arising in advance of anal, and scales sculptured. C. murchisoni, Ag., and other species from Lower Old Red Sandstone, Scotland. Acanthodopsis, Hancock and Atthey. Jaws with few large, laterally compressed, triangular teeth. A. Measures of Northumberland and Midlothian Acanthodes wardi, Eg. Skeletal parts of pectoral fin, nat. size. Coal Measures ; England, b, Hollow basal element ; r, Dermal rays ; s, Dermal spine forming an- terior border of fin (after Smith Woodward). /; Fig. 3S. Acanthodes gracilis, Beyr. Scales from the outer (.!,') and inner (/;) aspects, much enlarged. Lower Permian ; Germany, j wardi, EL and A., from Coal 22 PISCES class i Family 2. Diplacanthidae. Smith Woodward. Two dorsal fins. Free spines between paired fins conspicuous. Upper Silurian to Upper Devonian. Diplacanthus, Ag. (Ehadinacanthus, Traquair). Trunk fusiform, probably not much laterally compressed. Teeth minute or absent ; orbit with ring of four circumorbital plates. Pectoral fins large, and a median pair of stout spines fixed between these to the well-developed basal supports ; a single pair of free spines between the pectoral and pelvic fins. D. striatus, Ag., about 0*1 m. in length, and other species from the Lower Old Eed Sandstone of Scotland. D. horridus, Smith Woodward, from Upper Devonian, Scaumenac Bay, Canada. Ischnacanthus, Powrie (Ictinocephalus, Page). Much resembling Diplacanthus. but the inner pectoral spines wanting, and the jaws provided with a powerful dentition. A few large, smooth, conical teeth alternating with minute cusps. Scales smooth. /. gracilis, Egert. sp., from Lower Old Red Sandstone, Turin Hill, Forfarshire. Climatius, Ag. {Brack //acanthus, Egert.), (Fig. 39). Trunk fusiform and laterally compressed. Teeth minute or absent ; orbit with ring of four circumorbital plates. Fin spines remarkably broad and marked with coarse longitudinal ridges, sometimes with posterior denticles. Pectoral fins not much larger than the pelvic pair ; three or four pairs of free spines, resembling the fin spines, between the FlG - 39 - paired fins. C. reticu- Climatius scutiger, Bgerton. Lower Old Red Sandstone ; Forfarshire. /„/,„ \ ~ „,,,] r( Q ^,Uno^ Nat. size (after Powrie). UUUS, J±g., dllU U. SCUUgei , Egert. (Fig. 39), are known by nearly complete fishes from the Lower Old Red Sandstone of Forfarshire. Similar spines occur in the Passage Beds (Downtonian) of Here- fordshire, and in the Lower Devonian of Campbellton, New Brunswick. Euth acanthus, Powrie. Essentially identical with Climatius, but with narrower straight spines. Lower Old Red Sandstone, Forfarshire. Parexus, Ag. Much resembling Climatius, but the anterior dorsal spine enormously elongated and with large posterior denticles, P. incurvus, Ag., and P. falcatus, Powrie, from Lower Old Red Sandstone, Forfarshire. Order 3. ICHTHYOTOMI. Cope. 1 (Proselach ii, Doderlein.) Endoskeleton well calcified, but no membrane calcifications. Pterygoquadrate arcade movably articulated with the cranium. A T o circumorbital plates. Neural and haemal Beyrich, A'., Monatsb. Berlin Akad. 1848, pp. 24-33.— Br ongniart, C, Bull. Soc. Industrie Mm. (Saint Etienne), ser. 3, vol. IJ. livr. 4, 1888.— Cope, E. I)., Proc. Amer. Phil. Soc. 1S84, p. 0/2 - — Davis, J. H'., On the fossil Fish-remains of the Coal Measures in the British Islands. I. Pleuracanthidae (Trans. Roy. Dublin Soc. ser. 2, vol. XII.), 1889.— Doderlein, L., Zool. Anzeig. vol. 2^£&v' SUB-CLA» I SELACHII 23 arches of vertebral axis long and slender. Pectoral fins with long, segmented axis from which smaller cartilages diverge on either side ; pelvic /ins of male with appended clasper ; caudal fin diphycercal. Family 1. Pleuracanthidae. Cope. Body slender, but slightly depressed; mouth terminal. Teeth with two principal divergent rasps. Branchial arches provided with clusters of minute denticles. Dorsal fin elongate, low, continuous along the back from a point shortly behind the head; slender fin supports more numerous than the neural spines. Lower Carboniferous probably to Upper Triassic. The Pleuracanthidae occur in the coal-bearing strata of the Carboniferous system and in the Lower Permian of Europe and North America. One species is also known by a nearly complete skeleton from the Hawkesbnrv Formation of New South Wales. For the isolated teeth of Pleuracanthus various generic names have been proposed, e.g. Diplodus, Ochlodus, Aganodus, Pternodus, Triodus, Thrinacodus; for isolated spines, the generic names Compsa- Fig. 40. Restoration of Pleuracanthus gaudryi, Brongn. Coal Measures ; Commentry, Allier (after C. Brongniart). canthus, Orthacanthus, and Lophacanthus ; for the clustered denticles of the branchial arches, the name Stemmatias (Stemmatodus). Pleuracanthus, Ag. (Xenacanthus, Beyrich; ? Didymodus, Cope), (Figs. 40-4.')). Head broad, semicircular in front, and provided behind with a long, slender dermal spine, which is hollow, either rounded in section or antero-posteriorly compressed, and bears a double longitudinal series of recurved denticles (Fig. 42). Teeth (Fig. 43) with two large divergent cusps fixed on a stout common base, and frequently a small third cusp between these. Five branchial clefts laterally placed in advance of the stout and broad, arched pectoral girdle, of which the two halves are fused ventrally but separated dorsally. Pectoral fins large, articulated with the postero-inferior angle of the pectoral girdle, and consisting of a segmented axis fringed on either side by cartilaginous rays. Pelvic supports in the form of a pair of separate triangular cartilages; basi- 1T. 1889, p. lIZ.—Fritsch, A., Fauna der Gaskohle, vol. II. Prague, 1888-89.— Goldfuss, A., Neues Jahrb. l s 47, p. 404, and Beitrage zur vorweltlichen Fauna des Steinkohlengebirges, p. 23, pi. v. Figs. 9, 10. — Kner, R., Sitzungsb. k. Akad. Wiss. Wien, math. -naturw. CI. vol. 551, 1867. p. ">4<». with 10 plates. — Koken, /•". ^itzungsk Ges. naturf. Freunde, Berlin, 1889, p. 77. 24 PISCES CLASS I pterygium of pelvic fins segmented, fringed on one side with a series of carti- laginous rays, and continued behind into the spine-shaped clasper in the male. Two small anal fins, directly supported by the haemal arches. Caudal fin Fig. 41. c \l*"^ Fig. 42. Pleuracanthus (Orthacanthus) bohemicus, Fritsch. Lower Permian (Gas -Coal); Krot- schovv, Bohemia. A, Side view. B, Hinder view. C, Transverse section. Natural size. Pleuracantlnis (Xenacanthus) decheni, Goldf. Lower Permian; Braunau, Bohemia. x% J, Anterior portion of fish. B, Detached teeth, magnified (after F. Roemer). Fig. 43.' Pleuraco.nthu* {Diflodvs) lo- hemicus, Qnenst. Teeth in side view (^4), and hinder view (B). Lower Permian (Gas - Coal) ; Nyfan, near Pilsen, Bohemia. Natural size. separated both from the anals and from the dorsal. Skin probably destitute of shagreen. Complete skeletons are known from the Rothliegenden of Lebach, near Saarbrucken, in Rhenish Prussia, and of Braunau and Ruppersdorf in Bohemia; from the Lower Permian Gas-Coal of Bohemia ; from the Coal Measures of Commentry in France (Fig. 40) ; and from the Lower Hawkesbury Formation of New South Wales. Complete skulls have been found in the Coal Measures SUB-CLASS I SELACH1I 25 of Northumberland and in the Permian of Texas (Didymodus). Isolated teeth and spines are very abundant in the Carboniferous and Permian. Anodont acanthus, Davis. Dorsal spines without denticles. Carboniferous; England and Scotland. Order 4. PLAGIOSTOMI. Dumeril. Sharks and Rays. 1 Endoskeleton more or less calcified, but no membrane calcifications. Ptery go- quad rate arcade movably articulated with the cranium. Vertebral axis segmented. Paired fins with two or three short basal cartilages ; pelvic fins of male with appended claspers. According to the condition of their vertebral column, the Plagiostomi have been divided by Hasse into the four sub-orders of Diplospoiululi, Cyclo- spondyli, Asterospondyli, and Tectospondyli. Sub-Order A. , DIPLOSPONDYLI. Hasse. Notochord imperfectly segmented by vertical partitions. Gill clefts six or seven in number on each side. Teeth numerous, in several series. Upper Jurassic to Recent. Family 1. Notidanidae. Body fusiform, with a single unarmed dorsal and anal fin, and a large hetero- cercal caudal fin. Teeth with two or more sharply-pointed cusps. Upper Jurassic to Recent. Notidanus, Cuv. (Hexanchus, HepfancJuis, Midler and Henle), (Figs. 44, 45). Principal teeth consisting of a series of compressed cusps fixed upon a long base ; all the cusps in- clined in one direction, the anterior larger than the others, with or with- out small denticles at its base in front. Anterior teeth of the upper jaw clustered, awl-shaped ; a median symphysial series \\ in the lower jaw. Prin- cipal teeth of the upper jaw less laterally elon- gated, with fewer cusps than those of the lower jaw. Range from Upper Jurassic to present day. A. muensteri, Ag., repre- sented by a complete skeleton from the Lithographic Stone (Lower Kimmeridgian) of Solenhofen, 1 Bonaparte, C. L., Selacliorum tabula analytica (Mem. Soc. Sci. Nat. Xeufchatel). 1S39.- Davis, J. W., On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain (Trans. Roy. Dublin Soc. ser. 2, vol. I.), 1883.— Hasse, C, Das naturliche System der Elasmobranchier auf Fig. 41. Dentition of the Recent Indian Grey shark. Notidanus (Heptanehus) indicus. ■26 PISCES CLASS I Bavaria, and N. gracilis, Davis, by a smaller skeleton from the Upper Cretaceous of Sahel Alma, Mount Lebanon. Detached teeth from the Oxford Clay of England and Corallian of Wurtem- berg; from the Chalk of England (N. microdon, Ag.) and the Cretaceous of New Zealand (N. dentatus, Sm. Woodw.) ; and numerous species from Tertiary forma- tions (e.g. N. primigenius, Ag., Fig. 45). Chlamydoselache, Garman. Teeth with broad, back- wardly extended base, and the crown consisting of three slender, curved, subconical cusps, which are separated by a pair of rudimentary denticles. Wide distribution Isolated teeth in Pliocene of Tuscany (C. lawleyi, Fig. 45. Notidanus primigenius, Ag Lower tooth. Oligocene Weinheim, Hesse Darmstadt Natural size. in existing deep sea. Davis). Sub-Order B. CYCLOSPONDYLL Hasse. Vertebral centra in form of simple constricted cylinders pierced by the notochord. Teeth numerous^ triangular, and acuminate, simple or with small lateral cusps. Bare in the fossil state ; Upper Cretaceous to Recent. Family 1. Spinacidae. Midler and Henle. Spiny dog-fishes. Body fusiform to trihedral, somewl tat depressed. Mouth gently arched; snout obtuse. Gill clefts small, lateral ; spiracles large, behind the eye. Pectoral fins not notched at their origin and not produced forwards ; the two dorsal fins often armed with a spine ; anal fin absent. ' Upper Cretaceous to Recent. Centrophorus, Midler and Henle (Fig. 46). Dorsal fin spines present. Upper teeth erect, triangular, or narrow lanceolate, with a single cusp ; lower teeth triangular and compressed, with the apex much turned aside. Upper Cretaceous, Sahel Alma, Mount Lebanon (Spinax primaevus, Pictet). Recent. Acanthias, Risso (Centrophoroides, Davis), (Fig. 47). As Centrophorus, but teeth in upper jaw as in lower jaw. Upper Cretaceous, Sahel Alma, Mount Lebanon (Centro- phoroides latidens, Davis). Tertiary (A. radicans, Probst) and Recent. ( 'entrina, Cuv. Pliocene and Recent. Scymnus, Cuv. (Fig. 48). Xo dorsal fin spines. Upper teeth small, pointed ; lower teeth much larger, broad and compressed, triangular, erect or only slightly inclined laterally. Eocene to Recent. Echinorhinus, Blainv. (Goniodus, Ag.) Pliocene and Recent. Grundlage des Banes und der Entwickehmg ihrer Wirbelsaule. Jena, 1879, with Appendix, 1885. —Miiller, J., and Henle, J., Systematische Beschreibung der Plagiostomen. Berlin, 1841. — Jaekel, 0., Die eocanen Selachier vom Monte Bolca. Berlin, 1894. — Noetling, F., Die Fauna des samlan- dischen Tertiars (Abhandl. geol. Specialk. Preussen, vol. VI. pt. 3), 1885. — Probst. Beitrage zur Kenntniss der fossilen Fisclie aus der Molasse von Baltringen (Wurttemb. natnrw. Jahresh.), 1874, 1877. 187S, and 1882. Fig. 46. Vertebra (central double-cone) of Centrophorus. Upper Cre- taceous; Maastricht (after Hasse). Fig. 47. Acanthias roAicans, Probst. Tooth, x 2. Miocene (Molasse) ; Baltringen, Wiirtem- berg (after Probst.) Fig. 48. Scymn its triangulus, Probst. Tooth, x 2. Miocene (Molasse) ; Baltringen (after Probst.) ^ SUB-CLASs r SELACHI1 27 Sub-Order C. ASTEROSPONDYLI. Hasse. Vertebral centra when completely formed amphicoelous, strengthened by secondary plate's of calcified tissue which radiate outwards from the excessively constricted primitive cylinder. Fire gill clefts on each side. Two dorsal fins and our anal fin present. Lower Carboniferous to Recent. Family 1. Oestraciontidae. Agassiz. A a, odus i amosu-s, Ag. Carboniferous Limestone ; Armagh (after Davis). 1 /o. Dorsal fins each armed with a spine. Teeth numerous, mostly obtuse, never fused into continuous' plates ; several series simultaneously in function. Radiating plates of the vertebral centra few and short; vertebral column not calcified in the earlier forms. Lower Carboniferous to Recent. This family is characteristic of the later Palaeozoic and the Mesozoic formations ; it is represented in existing seas solely by one genus, Cestracion. OroduSj Ag. (Fig. 49), known only by obtuse elongated teeth. The dental crown raised in the middle, and its surface marked with more or less prominent wrinkles, which rise from each long margin or from a median longitudinal crest. Base of tooth very stout. 0. ramosus, Ag. (Fig. 49), and other species from the Carboniferous Limestone of Britain, Belgium, and Russia. Also numerous species in corresponding American formations. Campodus, Kon. (Agas- sizodus, St. J. and \Y. ; Arpagodus, Traut.). Teeth almost identical with Orodus, but distinguished by buttressed condition of the outer border of the crown. Symphysial series greatly enlarged, and fused. Carboniferous. Edestus, Leidy ; Campyloprion, Eastm. ; and Helicoprion, Karp., known only by their arched or coiled symphysial dentition. Carboniferous and Permian. Tristychius, Ag. (Ptychacanthus, Ag.), (Fig. 50). Dorsal fin spines with a few sharp longitudinal ridges distally, three only — -one upon the front margin and one on each side — extending far downwards. Teeth probably as in Sphenacanthus. T. arcuatus, Ag. Carboniferous. Sphenacanthus, Ag. Teeth rather high-crowned, with a large principal cusp and smaller lateral cusps diminishing in size outwards, more or less marked by superficial wrinkles; base depressed, forming a slight expansion back- Fig. 50. wards. Notochord persistent. Dorsal fin spines marked Tristychius arcuatus w j t h r0Dus t longitudinal ridges, fti part nodose; posterior shagreen-scale (/,'), and denticles small and numerous, m two series, one upon each (C Lo^Va;S',l! lateral margin of the flattened or slightly concave posterior c /; size. ferous Stock) Scotland (after s. face. Few minute comb-shaped shagreen granules. costellafus, Traquair sp., known by nearly complete fish from Calciferous Sandstones (Lower Carboniferous) of Eskdale. Dumfries. 28 PISCES CLASS I S. hybodoides, Egert. sp., represented by fin spines and teeth in English, Welsh, and Scottish Coal Measures. Hybodus, Ag. (Meristodon, Ag.), (Fig. 51). Teeth and dorsal fin spines almost as in Sphenacanthus ; but double series of denticles on hinder face of fin -spine median, not laterally placed. Symphysial teeth few and relatively large. Notochord persistent, but ver- tebral arches calcified. One or two large hook-shaped, semi-barbed dermal spines (Sphenonchus) immediately behind each orbit, at least in the male. Shagreen sparse, consisting of small conical, radiately grooved tubercles, which are sometimes fused into groups of three. Numerous species ranging from the Trias to the Lower Cretaceous. Teeth of H plicatilis, Ag. (Fig. 51, A), abundant in the Muschelkalk. Nearly complete skeletons from the Lower Lias of England (H delabechei, Charles- worth ; H. reticulatus, Ag., Fig. 51, B) and the Upper Lias of Wurtemberg (H. hauffianus, Eb. Fraas). Fine skulls from Wealden, Pevensey Bay, Sussex (H basanus, Egert.). Acrodus, Ag. (Thectodus, Plieninger), (Fig. 52). A genus only differing from Hybodus in the rounded, non-cuspidate character of the teeth. Common Fig. 51. Teeth of Hybodus. A, H. ■plicatilis, Ag. Muschel- kalk ; Laineck, near Bayreuth. B, H. reticulatus, Ag. Lower Lias ; Lyme Regis, Dorsetshire. C, H. polyprion, Ag. Lower Oolite (Dogger) ; Stonestteld, < ►xfordshire. Fig. 52. Acroda* anningiae, Ag. Dentition, 1/3 natural size. Lower Lias ; Lyme Regis. A, .Symphysis. B, Detached tooth, seen from side and above, natural size. in the Triassic and Jurassic, and ranging to the Upper Cretaceous. A. gaillardoti, Ag., teeth from Bunter, Muschelkalk, and Keuper of Germany and France. A. minimus, Ag., common in European Keuper and Rhaetic. A. anningiae, Ag. (Fig. 52), and A. nobilis, Ag., known by fine specimens from the Lower Lias, Lyme Regis. A. levis, Sm. Woodw., teeth from English Gault. Palaeobates, Meyer. Teeth depressed, rounded, without lateral denticles and not keeled. European Triassic. Aster acanthus, Ag. (Strophodus, Ag. ; Curtodus, Sauvage), (Figs. 53, 54). Principal teeth elongated, irregularly quadrate, with slightly arched but flattened crown ; symphysial teeth few, smaller but relatively large, much SUB-CLASS I SELACHII ■29 arched, without lateral denticles, and longitudinally keeled ; all superficially marked by reticulating ridges. Xotochord persistent. Head spines as in Hyhodus and Acrodus. Dorsal fin sj^ines marked by stellate tubercles, sometimes partly fused into longitudinal ribs ; also bearing a median longitudinal double series of tubercles on their hinder face. Middle and Upper Jurassic. A. ornatissimus, Ag. (Strophodus reticulatus, Ag.), (Fig. 54), well known from Corallian, Oxfordian, and Kimmeridgian of Europe. / Palaeospinax, Egerton. Dentition compara- tively specialised ; the few anterior teeth high- crowned and prehensile, with a single pair of lateral denticles ; posterior teeth low-crowned, with two or three pairs of lateral denticles reduced to minute beads. Vertebrae very slightly asterospondylic. Dorsal fin spines smooth and enamelled, without posterior denticles. Shagreen fine and dense ; no head spines. P. priscus, Egert., known by nearly complete specimens from Lower Lias, Lyme Regis. Fragments of other species from Upper Lias, Wiirtemberg. Fig. -"-4. Tooth of Asteracanihus (Strophodus reticulatus, Ag.), inside view and upper view. Corallian; Tonnere, Yonne. Fir.. 53. Asteracanthus ornatissirwus, Ag. Dorsal fin-spine, lateral view (A), posterior view (/,'). and detached tubercle enlarged (' ). Portlandian ; Soleure. Switzerland. Syneclwdus, Smith Woodward (Fig. 55). Almost identical with Palaeo- spinax, but teeth with more numerous lateral denticles, and vertebrae more distinctly asterospondylic. Complete jaw of S. dubrisiensis, Mackie sp. (Fig. 55), and greater part of skeleton of same species known from the Lower Chalk of England. Teeth of other species from various Cretaceous formations in Europe, Cretaceo-Tertiary of Xew Zealand and Patagonia, and one (S. clarki, Eastman) from the Maryland Eocene. Cestracion, Cuv. (Heterodontus, Blainv. : Drepanephorus, Egert.), (Figs. 56, 57). Symphysial teeth small, numerous and prehensile, with a median cusp and one pair of lateral denticles ; lateral teeth in oblique series, with faintly keeled and finelv rugose crown. Vertebrae asterospondylic. Dorsal tin fqRb ^ ■SB SUB-CLASS T SELACHII 31 spines smooth, without posterior denticles the Lithographic Stone (Upper Jurassic) of Bavaria (C. falcifer, Wagn., Fig. 56) and the Chalk of England (so-called Drepane- phoms canaliculars, Egert.). Teeth from Lower and Middle Eocene of England and Belgium. Existing in Australian and other seas. Nearly complete skeletons from Familv 2. Scylliidae. and Henle. Miiller Fig. 57. Lower jaw of Recent Port Jackson Shark, ' 'estrcu Cuv. Australia. Dorse I fins without spines, the (interior situated above or behind the pelvic fins. Teeth small, numerous, and pointed, sere rat series being generally in function. Vertebrae with eight stout radiating plates. Upper Jurassic to Recent, but fossils rare. Palaeoscyllium, Wagn. Anterior dorsal fin opposite pelvic pair, and posterior dorsal arising in advance of anal, which is small. P. formosum, Wagn., and P. minus, Sm. Woodw., known by nearly complete fishes from Lithographic Stone, Bavaria. Scyllium, Cuv. (Thyellina, Ag.), (Fig. 58). Origin of anal fin always in advance of that of posterior dorsal fin. Teeth delicate with a high middle cusp and generally one or two small lateral denticles. Nearly complete fishes from the Upper Cretaceous of Westphalia (>'. angustum, Ag. sp.) and Mount Lebanon (S. elongatum, Davis sp.) ; also numerous detached teeth from the Chalk and Tertiaries (Fig. 58). Recent. Pristiurus, Bonap. As Scyllium, but with a series of small flat spines on each side of the upper edge of the caudal tin. Probst') 1 " PU(aftel P- nmse h S m - Woodw., a small species from the Lithographic Stone of Eichstadt, Bavaria. Recent. Mesiteia, Kramberger. Snout produced. Teeth minute and tricuspid. Anterior dorsal fin above or behind pelvic pair; anal fin much extended. Tail excessively elongated, without dermal scutes or spines. Shagreen absent or very delicate, and lateral line supported by a series of calcified rings as in Chimaeroids. M. emiliae, Kramberger, from Upper Eocene, Monte Bolca, near Verona; M. sahel-almae, Pict. and Humb. sp., from Upper Cretaceous, Mount Lebanon. Chiloscyllium, Mull, and Henle, and Gingly mo stoma, Mull, and Henle (Plicodus, Winkler ; Acrodobatis, Leidy). Tertiary and Recent. Family 3. Carchariidae. Miiller and Henle. Dorsal fins without spines, the anterior situated opposite to the space between the pectoral and pelvic fins. Teeth hollow, pointed cud triangular, with smooth or Fi<;. 58. Scyllium distans, Probst. Tooth, x 2. Miocene (Molasse) ; 32 PISCES CLASS I serrated lateral borders. Vertebral centra with four radiating ridges which widen outwards. Tertiary and Eecent. Hemipristis, Ag. (Dirrhizodon, Klunzinger), (Fig. 59). Principal teeth large, triangular and compressed, with coarsely serrated edges; anterior lower teeth slender, subulate, inwardly curved, and without denticulations or with one or two minute points at the base. H. serra, Ag. (Fig. 59), common in the Miocene of Europe and in the Tertiary Phosphate Beds of South Carolina and Maryland Miocene. H. curmtus, Dames, from Oligocene, Birket- el-Qurun, Egypt. One existing species. Galeocerdo, Miiller and Henle (Fig. 60). Teeth oblique, serrated on both margins, with a deep notch posteriorly. Eocene to Eecent. G. latidens, Ag., Fig. 59. Hemipristis serra, Ag Neudorfl, Hungary. Miocene ; A, Tooth of Galeocerdo adunms, Ag. Miocene (Molasse) ; Pfullendorf, Baden. B, Section of vertebra of Galeocerdn. Miocene (Molasse); Baltrmgen (after Hasse). Fig. 61. Gale »s affinis, Probst. Miocene (Molasse) ; Bal- tringen (after Probst.). from Bracklesham Beds and Maryland Miocene species, apparently ranging to the Pliocene. triqueter, East., from the American Miocene. Alopiopsis, Lioy, and Pseudogaleus, Jaekel. Upper Eocene, Monte Bolca, near Verona. Galeus, Ag. (Protogaleus, Molin.), (Fig. 61). G. aduncus, Ag. (Fig. 60, A), G. contortus, Gibbes, and G. Nearly complete fishes from Teeth small and oblique, the margins only serrated at the base, and a deep notch pos- teriorly. Eocene to Recent. Carcharias, Cuv. (Fig. 62). Teeth mostly oblique and tri- angular, without lateral denticles, usually different in the two jaws. The lateral edges serrated to the apex (Prionodon, Miiller Probst. D, Carcharias (Prionodon) \ similis] Probst. Miocene an( J Henle) or Only at the base (Molasse); Baltringen (after Probst.). , „ . , T j t T \ "L (Hypoprion, M. and H.), or sharp- edged but not serrated (Scoliodoii, Physodon, M. and H.), sometimes also erect and sharp-edged (Aprionodon, Gill). Tertiary and Recent. Sphyrna, Raf. (Zygaena, Cuv.). Hammerhead sharks. Tertiary and Recent. S. prisca, Ag. Mustelus, Cuv. ; Triaenodon, Triads, M. and H. Recent. Fig; 62. A, Carcharias (Aprionodon) freqiiens, Dames. Eocene; Birket-el-Qurun, Egypt (after Dames). 11, Carcharias (Hypo- prion) singvZaris, Probst. C, Carcharias (ScOliodon) kraussi, Family 4. Lamnidae. Miiller and Henle. Dorsal fins without spines, the anterior situated opposite to the space between the pectoral and pelvic fins. Teeth, pointed and usually large, with or without lateral SUB-CLASS I SELACH1I 33 Pig. 63. Orthacodus longidens, denticles, and the pulp cavity completely filled with vasodentin*. Vertebral centra with eight bifurcating plates which radiate outwards. Upper Jurassic to Recent. Orthacodus t Sm. Woodw. (Sphenodus, Ag., non Gray, nee Lund), (Fig. 63). Teeth very slender and erect, compressed, without lateral denticles • the root broad and depressed, simple. 0. longidens, Ag. sp. (Fig. 63), and other species are Upper Jurassic. Apparently also a Lower Cretaceous genus. Scapanorhynchus, Sm. Woodw. {lihinognathus, Davis non Fairmaire ; 1 Mitsukurina, Jordan). Body slender, snout much elongated. Second dorsal fin small, opposed to a much extended anal fin ; caudal fin much elongated, inferiorly notched near the extremity. Teeth as in Od out as pis. Complete ^n sp ; w hi t '', ni7; , . . _ *■ Bollert, wurtemberg. skeletons of S. lewisi, Davis sp., and S. elongatus, Sm. Woodw., from the Upper Cre- taceous of Sahel Alma, Mount Lebanon. Detached teeth (S. rhaphiodon, Ag. sp.) in Upper Cretaceous of Europe, probably also in North America, India, and New Zealand. Apparently living in the deep sea off Japan (Mitsukurina owstoni, Jordan). Odontaspis, Ag. (Triglochis, M. and H. ; Otodus, Ag. in part.), (Fig. 64). Snout not much elongated. Second dorsal fin and the anal of equal size, scarcely smaller than the first dorsal. Side of tail without keel. Teeth with a slender principal cusp, with sharp lateral edges, flattened outer face, and convex inner face, also one or two pairs of small lateral denticles ; root large and bifurcated. Upper Fig. 64. Odontaspis cuspidata, Ag. sp. Oligoeene ; Weinheim, near Alzey. Fig. 65. Vertebra of Lamna, in front (A) and side view (£), and in vertical median section (Q. Nat. size. A, B, From Oligoeene of Flonheim. C, From London Clay, Sheppey. Cretaceous, Tertiary and Recent. 0. hronni, Ag. U. Cretaceous, Maastricht and Ciply. 0. elegans, Ag. sp., and 0. cuspidata, Ag. sp. (Fig. 64), from Lower Tertiaries. Otodus, Ag. (Figs. 65-67). Very robust teeth with stout lateral denticles, VOL. II D 34 PISCES CLASS I of rather doubtful relationships. Most species described under this name referable to Lamna and Odontaspis. Cretaceous and Eocene. Lamna, Cuv. Second dorsal fin and the anal very small. Side of tail with keel. Teeth as in Odontaspis, but the principal cusp usually somewhat broader and the lateral denticles larger. Very abundant in the Chalk, Tertiaries, and existing seas. Oxyrhina, Ag. (Fig. 68). Only differing from Fig. 66. Otodus appendicu- latiis, Ag. Planer ; Quedlinburg. 1'h.. 67. Otodus obliquus, Ag. External aspect of tooth. Eocene ; Sheppey. Fig. 6S. Oxyrhina plicatilis, Ag. Mio- cene ; Neudorfl, Hungary. Lamna in the teeth lacking lateral denticles. Cretaceous to Recent. 0. manielli, Ag., the commonest Cretaceous species both in Europe and North America, the nearly complete dentition known from Kansas. 0. desori, Ag., chiefly Lower Tertiary ; 0. hasfalis, Ag., chiefly Upper Tertiary. Alopecias, M. and H. Tertiary and Recent. Cor ax, Ag. (Fig. 69). Known only by low triangular teeth with sharp, serrated edges, and a large root. raon in the Middle and Upper Cre- taceous. C. prist oi I onf us, Ag., from Maastricht, North Africa (F12;. 69), and Fig. 69. Covax pristodontus, Ag. Upper Chalk ; < >asis of Dachel, Libyan Desert. Carcharodon megalodon, Ag. .Miocene; Malta. supposed Eocene of Alabama. C.fakatus, Ag., European and North American Cretaceous. Carcharodon, M. and H. (Fig. 70). Second dorsal fin and the anal very small. Side of tail with keel. Teeth very large and triangular, with serrated lateral edges, flattened outer face, convex inner face. One Upper SUB-CLASS I SKLACHII 35 Cretaceous (C. longidens, Pillet) and one existing species (C. rondeleti, M. and H.) ; the others Tertiary. G. megalodon, Ag. (Fig. 70), and allied species are represented by very large teeth in the Tertiary and later formations of nearly all parts of the world, also on the bed of the existing oceans. Cetorhinus, Blv. (Selache, Cuv.). Teeth very small and conical, without lateral denticles. Claspers of male with horn -shaped spines, which have been found in the Pliocene of England and Belgium. The existing " basking shark." Sub-Order D. TECTOSPONDYLI. Hasse. Vertebral centra when completely formed amphicoelous, strengthened by secondary ■plates of calcified tissue which are concentric with the constricted primitive cylinder. Five gill clefts on each side. Anal fin absent. Bod// usually depressed, with very large pectoral fins for mi rig a "disk." To the Tectospondyli belong the still existing rays, monk-hshes, and saw- fishes, perhaps also the Palaeozoic families of Cochliodontidae, Psammo- dontidae, and Petalodontidae. Family 1. Cochliodontidae. Owen. Palaeozoic fishes with few convex teeth, which are more or less arched, hollowed at the base, punctate on the crown, and often marked with obtuse transverse folds or grooves. A large posterior dental plate, above and below on each side, a smaller anterior dental plate, and one or more series of separate smcdler anterior teeth. Head and perhaps also the pectoral fins armed with paired tuberculated spines, Carboniferous and Permian. Our knowledge of this most remarkable Upper Palaeozoic family is still very incomplete. Of two genera (Helodus and Menaspis) the impression of the trunk is known ; of all the others only teeth or fin spines and, very rarely, complete jaws occur. According to Jaekel we may place here the un- symmetrical Ichthyodorulites, with tubercles, bosses, or spines and destitute of a root, which have been described under the names of Oracanthus, Pnigeacanthus, Cladacanthus, Platy acanthus, Gamps- acanth us, Physonemus, Stichacanthus, etc. Owen has pointed out that the dentition in the typical genera Cochliodus and Streblodus corresponds with that of a Cestraciont, but differs from the latter in the fusion of two or more transverse series of teeth into continuous plates. Smith Woodward has thus proposed to place the typical Cochliodontidae near the Cestraci- ontidae, removing Menaspis to the Chimaeroid family of Squaloraiidae. Cochliodus, Ag. (Fig. 71). Two strongly arched dental plates on each ramus of the mandible; the posterior one very large, with a broad median area bounded in front and behind by an oblique transverse furrow ; the anterior plate comparatively small, rhomboidal in shape. Symphysial series Cochliodas contortus, Ag. Dentition, :; 4 nat. size. Carboniferous Limestone; Armagh. .1. Large posterior tooth. J:, Middle tooth : anterior teeth wanting. 36 PISCES CLASS I of. C. latus, Leidy, from Keokuk Limestone of Mississippi Valley, the largest known species, originally described as Helodus coxanus, Newb. Lower Carboni- ferous ; Ireland, England, Belgium, and North America. Streblodus, Ag. As Cochliodas, but hinder tooth with two to three broad, oblique, transverse folds. S. oblongus, Ag., and S. colei, Davis, from Carboni- ferous Limestone, Armagh. Other species from England and North America. Sandalodus, Newberry and Worthen (Trigonodus, Faticinodus, N. and W. ; Orthopleurodus, St. John and Worthen). Supposed upper teeth triangular, thick, slightly inrolled. Supposed lower teeth more strongly inrolled ; the hinder one subtriangular or twisted and elongate, with one to two diagonal ridges, and anteriorly coiled in a distinct whorl ; the anterior one short, truncated in front, strongly inrolled. Carboniferous ; Ireland, England, Belgium, and North America. Deltoptuchius, Ag. ; Chitonodus, St. John and Worthen ; Poecilodus, Ag. ; Deltodus, Ag. (Taeniodus, St. J. and W.) ; Xystrodus, Ag. Carboniferous Lime- stone ; Europe and North America. Psephodus, Ag. 1 (Fig. 72). Large rhombic or rhomboidal teeth, convex and gently arched, with crenulated border. With these large teeth are A Fig. 72. Psephodiis iiaiijinis, Ag. A, Three teeth in connected series, nat. size, from the Carboniferous Limestone of Armagh (after Davis). B, Associated upper teeth from remains of head found in Calciferous Sandstones. East Kilbride, Lanarkshire, b, Large tooth somewhat broken ; c, Small tooth identical with Hdodus rudis, M'Coy; d, Slender teeth identical with Helodus planus, Ag. ; e, Helodont teeth; f, g, Teeth identical with Lopltodus didymus and L. laevissimus, Ag. sp. (after Traquair). sometimes associated more numerous transversely elongated small teeth, of which isolated examples have been described under the names of Helodus, Lophodus, and Aspidodus. Carboniferous Limestone ; Europe, India, and North America. Pleuroplax, Sm. Woodw. (Pleurodus, Hancock and Atthey, nan Wood, nee Harlan). Teeth with feeble antero- posterior ridges, and the antero- and postero-lateral borders indented between these ridges. These teeth some- times associated with others of the Helodus-type. At least one dorsal fin, with an unornamented spine. P. rankinei, H. and A., from English Coal Measures. Other species from Upper and Lower Carboniferous of Europe and North America. Menaspis, Ewald, emend. Jaekel 2 (Dichelodus, Giebel ; Chcdcodus, Zittel), 1 Traquair, R. H., Trans. Geol. Soc, Glasgow, vol. VII. 1885, p. 392. 2 Jaekel, 0., Ueber Menaspis (Sitzungsb. naturf. Freunde, Berlin, 1891, p. 115). — Reis, 0., Ueber die Kopi'stacheln von Menaspis armala, Munich, 1891. SUB-CLASS I SELACHII 37 (Fig. 73). Head and back covered with longitudinal series of tuberculated or spiny, partially keeled placoid scales A and small shagreen granules. On each side of the front portion of the head a triangular spine, provided with a broad, hollow base and covered with tubercles of dentine. Further back on each side three smooth, thin, arched spines fixed by a conspicuous basal process in the skin of the head, curved inwards, and apparently consisting of calcined Cartilage ; the middle pair 01 Zittel). Dentition from above {A), and below (B), nat ,i ,i • ■, size. Kupferschiefer ; Glucksbrunn, Thurineia. these spines more than twice as long as the others. Dentition consisting of one pair of Cochliodont teeth in each jaw (Fig. 73). M. armata, Ewald, from Kupferschiefer of Germany. Pig. 73. Menaspis armata, Ewald (Chalcodus permianus, Family 2. Psammodontidae. De Koniiuk. Known only by large, flat, or slightly arched teeth, with punctate or finely rugose grinding surface. The teeth are of quadrate or oblong shape, and were originally arranged in one, two, or more longitudinal series. Lower Carboniferous. Psammodus, Ag. (Homalodus, Astrabodus, Davis), (Fig. 74). Teeth quadrangular, with relatively thick base, smooth or feebly striated on the attached surface, arranged in the jaw in paired longitudinal series. P. rugosus, Ag. (Fig. 74), from Carboniferous Limestone of Ireland, Scotland, England, Wales, and Belgium. Allied species in Russia and North America. A rchaeobatis, Newberry. Teeth scarcely distinct from Psammodus. An associated group of A. gigas, Newb., known from St. Louis Limestone, Greencastle, Indiana (Ann. New York Acad. Sci. vol. i. 1878, p. 190). Copodus, Davis (Mesogomphus, Ehymodus, Characodus, Pinacodus, Davis). Comparatively small median teeth, narrower in front than behind, divided into two unequal parts by a transverse suture. C. cornutus, Davis, and allied species from Carboniferous Limestone of Ireland, England, and North America. Fig. 74. Psammodus rugosus, Ag. Imperfect tooth from above (A), and in transverse section (B), nat. size. Carboniferous Limestone ; Armagh. Family 3. Petalodontidae. Newberry and Worthen. Teeth aider o-posteriorly compressed, transversely elongated, arm aged in longitudinal and transverse rows and forming a pavement. Crown enamelled, more or less bent backwards, either with a sharp cutting edge or very obtuse, the anterior face convex, the posterior face concave ; root separated from the crown by a constriction, usually with enamel folds immediately above it. Carboniferous and Permian. Of this extinct family, Janassa is the only genus of which more than the dentition is known. This fish exhibits a ray -shaped trunk covered with smooth, rounded shagreen granules ; the large pectoral fins extend forwards 38 PISCES CLASS I /; to the head, and the pelvic pair are separated from them by an interspace ; the tail is slender, and mouth narrow. There are no fin spines. . Petalodus, Owen (Chomatodus, Ag. in part; Sicarius, Leidy ; Antliodus, Newb. \ Lisgodus, St. John and Worthen), (Fig. 75). Teeth much antero- posteriorly compressed and transversely elongated. Crown leaf- shaped, with cutting edge and sharp basal margin with enamel folds ; root long and comparatively slender, truncated below. P. acuminahcs, Ag. sp., and other species from the Carboniferous Limestone of Eng- land, Scotland, Ireland, Belgium, Russia, and North America. Rare in the Coal Measures of North America. Petalorhynchus, Newb. and Worth. Dentition consisting of six transverse rows of three acumi- verse n section I ( l B)7i/I n£t. size, "coal nate cutting teeth with undivided root. Carboni- Newberry^ Spri,1 ^ eld ' Illinois ( atter ferous Limestone; Europe and North America. Janassa, Miinster (Dictaea, Byzenos, Minister ; Climaxodus, M'Coy ; Peltodus, Newb. ; Tanaodus, St. John and Worthen), (Fig. 76). Dentition consisting of narrow and elongated teeth with a reflexed punctate crown, which are arranged in five to seven longitudinal, and seven transverse rows, three on either side of the symphysial series. The oral Petalodus Fig. 7."'. alleghaniensis, Leidv. A Pig. 70. Janassa bituminosa, Schloth. sp. Kupferschiefer ; Gliicksbrunn, Thuringia. A, Upper and lower dentition. B, Cross-section, C, Tooth from in front, and D, from behind. E, Dermal tubercles, enlarged. cutting margin is formed entirely by the anterior face of the crown, which is bent backwards sharply and overlaps the next older tooth in front, which serves as a support. The long, tapering root of each tooth is much compressed antero-posteriorly, slightly arched, transversely ridged on the convex anterior face, smooth on the concave hinder face. Skin covered with oval or quadrate, smooth, shagreen granules. /. bituminosa, Schloth. sp. (Fig. 76), represented by important specimens from the Kupferschiefer of Hesse and Thuringia, also from the Marl Slate of Durham. Detached teeth SUB-CLASS I SELACHII 3!> I: of other species (so-called Climaxodus, etc.) from Upper and Lower Carboni- ferous of England, Scotland, Ireland, and North America. Fissodus, St. John and Worthen. Car- boniferous Limestone ; North America and Scotland. Glossodus, M'Coy ; Mesolophodus, Sm. Woodw. Carboniferous Limestone; Ireland. Polyrhizodiu Fig. 77. magnus, M'Coy. Tooth in front size. )• Fig. 78. Poll/rhlZOdus, M Coy (DactyloduS, view (.4), and transverse section|(£), i/ 2 nat. siz \ /-r,. r-~\ m m i vi Carboniferous Limestone ; Armagh (after M'Coy Newb.), (Fig. 77). Teeth robust, with a tumid crown tapering to a transverse cutting edge, and the root much sub- divided. P. magnuSj M'Coy, and other species from the Car- boniferous Limestone of Ireland, England, Russia, and North America. Ctenoptychius, Ag. i allopristoaus pec- r J > o tinatus, Ag. sp. (oai (Ctenopetalus, Harpacodus, Measures ; Scotland. v , . t\ • ' c< Petalodopsis, Davis ; ber- ratodus, de Koninck. Teeth small, antero-posteriorly compressed, with sharp serrated ed, Squatina fraasi, Probst. Tooth, x 2. Miocene (Molasse); Baltringen. Fig. 81. Longitudinal section of the tectospon- dylic vertebral column of Squatina angelus, Linn, cli, Notochord ; d, Cal- cified double-cone (basis of centrum) ; ir, Intervertebral space; w, Vertebral centra with concentric calcified rings (after Hasse). fragmentary remains of S. cranei, Sm. Woodw., occur in the English Chalk. Numerous teeth and vertebrae in the Tertiary. S. Occident alls, East., from the Maryland Miocene. Famih ; 5. Pristiophoridae. Giinther. Trunk fusiform. Snout much elongated and flattened, without lateral cartilages, but fringed on each border with pointed dermal teeth. Branchial clefts lateral. The two dorsal fins without spines. Upper Cretaceous to Recent. Pristiophorus, M. and H. Miocene to Recent. An undescribed form in the Upper Cretaceous of Mount Lebanon (Smith Woodward). Family 6. Pristidae. Gunther. Saw-rishes. Trunk elongated, slightly depressed. Pectoral fins rather large, 'united with the head, but not extended to the long, depressed, sword-like rostrum, strengthened with lateral cartilages, and armed with a row of large, dermal teeth on each lateral border. Branchial clefts on the ventral surface. Teeth of the mouth minute and obtuse. Upper Cretaceous to Recent. Sclerorhynchus, Sm. Woodw. Teeth of rostrum comparatively small and not fixed in sockets. Rostrum thus resembles that of Pristiophorus, but differs from the latter and agrees with Pristis in the great development of a pair of lateral cartilages. S. atavus, Sm. Woodw., known by nearly complete skeletons from Upper Cretaceous, Mount Lebanon. Pristis, Latham. Teeth of rostrum peg-like, firmly implanted in sockets of calcified cartilage. Middle Eocene (Bracklesham Beds) to Recent. Propristis, Dames. Rostral teeth as in Pristis, but not implanted in cartilage. Upper Eocene ; Birket-el-Qurun, Egypt. Family 7. Rhinobatidae. Midler and Henle. Trunk depressed, but elongated. Pectoral fins large, connected with the head, but the cartilaginous rays not reaching the end of the somewhat elongated snout. Branchial clefts on the ventral side. Teeth small and obtuse. Tail robust, with two dorsals and a large caudal fin. Upper Jurassic to Recent. SUB-CLASS I SELACHII 41 Bkinobatus, Bloch (Euryarthra, Ag. ; Spathobatis, Thioll.), (Fig. 82). Dorsal fins without spines. Skin with small shagreen granules. Com- plete skeletons from the Litho- graphic Stone of Bavaria and France, the Upper Cretaceous of Mt. Lebanon and Italy, and the L T pper Eocene of Monte Bolca. Also later Tertiary and Recent. Asterodermus, Ag. Dorsal fins with small spines. Sha- green granules rather large, stellate. A. platypterus, Ag., a small species from the Litho- graphic Stone of Bavaria. Belemnobatis, Thiolliere. Lithographic Stone; Cerin, Ain, France. Trygonorhina, Platyrhina, M. and H. Eocene to Recent. Family 8. Tamiobatidae. This family, represented by the unique Tamiobatis vetustus, Eastman, from the Devonian or Lower Carboniferous of Ken- tucky, is of uncertain system- atic position, but intermediate between existing sharks and rays. Family 9. Rajidae. Midler and Henle. Skates. Trunk much depressed, form- ing a broad, usually rhombic disk with the pectoral fins, which extend from the snout to the pelvic fins. The latter fins with a strong, un- segmented, cartilaginous ray in front. Teeth small, with bifur- cated root and rhombic crown, forming a close pavement in each jaw. Tail very slender, without . 7 ,7 7 7 r 77 Stone); Eiehstailt, Bavaria. (From a specimen 1", m. Spines, and the Caudal fin small Or the Palaeontological Museum, Munich.) absent. Skin with small, pointed shagreen granules and larger, scattered, spinous, placoid tubercles. Upper Cre- taceous to Recent. Fig. -J. Uhindbatus miraMis, Wagn. Upper Jurassic (Lithographic lone in 42 PISCES CLASS I Cyclobatis, Egerton. Disk circular or oval, and tail very short, without median fins. Eays of paired fins few and well-spaced, the pectorals united in front of the head. Pelvic arch with very large pre-pubic processes. C. oligo- dactylies, Egerton, from Upper Cretaceous, Hakel and Hajoula, Mount Lebanon. Raja, Cuv. (Actinobatis, Ag.), (Fig. 2). Upper Cretaceous (Mount Lebanon) to Recent. Dermal tubercles of existing II. clavata, Linn., in Pliocene Crags of Xorfolk and Suffolk. Family 10. Torpedinidae. Miiller and Henle. Torpedoes. Traul: much depressed, forming a broad and rounded dish with the pectoral fins, which do not extend forwards to the broadly rounded anterior end of the head. Tad six ni and fleshy, with well -developed dorsal and caudal fins. Skin naked. An electric organ between the pectoral fins and the head. Eocene to Recent. Torpedo, Dumeril (Narcobatis, Blv.). Sometimes supposed to be represented by skeletons in Upper Eocene of Monte Bolca, but doubtful. Recent. Narcine, Henle. Upper Eocene of Monte Bolca, and Recent. A Family 1 1 . Trygonidae. Miiller and Henle. Sting-rays. Trunk much depressed, forming a disk with the very broad pectoral fins, which meet In front of the snout, and constitute the anterior border of the head. Tail very slender, sharply separated front tin disk, the dorsal fins usually replaced by several stout imbricating spines of vasodentine, which are antero-posteriorly compressed and armed with a row of recurred hooklets on each lateral border. Teeth small, rhombic or polygonal, with bifurcated root, and forming a close pavement. Skin naked, with large conical plates of vasodentine, sometimes fused into groups, usually raised into a short spine. Tertiary and Recent. Trygon, Adanson (Trygonobatus, Blv. ; Alexandrinum, Molin), (Figs. 83, 84). Tail elongated, with long, flattened dorsal spines. Dermal plates of very variable form and size. T. gazolae, Ag. ; T. {Alexandrinum) molini, Zigno ; T. zignoi, Molin, known by nearly complete skeletons from the Upper Eocene of Monte Bolca. Isolated dermal plates (Fig. 84) have been described as refer- able to Raja, Acipenser, Dynatobatis, Larrazet, and Acanthobatis, Larr. Taeniura, Uroloph us, M. and H. Upper Eocene (Monte Bolca) and Recent. XiphoirygoD, Cope (Heliobatis, Marsh). Resembling Trygon, but teeth cuspidate. X. acutidens, Cope, known by complete skeletons from Eocene Green River Shales *» b f cie \ ™\ siz ^ » -, TT x . (Molasse); Baltnngi oi Wyoming. Oacobatis, Leidv. Dermal tubercles. Pliocene ; Idaho in- Fig. S3. Trygon rugosus, Probst. Tooth terior (A), posterior (B), and lateral (C), aspects, enlarged, and the same nat. size (D). Miocene (Molasse) ; Baltringen (after Probst.). Fig. 84. Trygon (Acanthobatis) tuber- ulosus, Probst, sp. Dermal Miocene gen. SUB-CLASS I SELACHI1 43 Family 12. Myliobatidae. MilUer and Henle. Eagle-rays. Trunk much depressed, forming a broad disk with the very large pectoral fins, which are interrupted at the sides of the head, but reappear as one or a pair of small cephalic fins at the extremity of the snout. Tail very slender, with one or several flattened spines behind the single dorsal fin. Teeth rather large, forming a dost pari an at in both jaws. Skin naked. Cretaceous (1), Tertiary and Recent. Most of the surviving genera of this family are represented in the Tertiary by isolated teeth and spines, or by the complete dentition. 1 Ptychodus, Ag. (Aulodus, Dixon), (Figs. 85, 86). Known only by the dentition and vertebrae, and hence of uncertain systematic position. Teeth quadrangular, with a raised crown, which is transversely or radially ribbed, and sharply separated by a constriction from the smaller, Fig. 85. odus^olygyrus, Ag. Tooth, oral and posterior views. tat. size. Greensand ; Regensburg. Fir,. 86. Ptychodus decurrens, A.u. Diagram of arrangement of teeth in upper (A), and lower (II) jaws, much reduced. I. own- Chalk ; England (after Smith Wood- ward). smooth root.l The teeth are solid, and the ganodentine investing the crown is thick. They are arranged in about thirteen antero-posterior series (Fig. 86). In one jaw, presumably lower, the median series of teeth is the largest, and the lateral rows are dis- posed symmetrically, diminish- ing in size outwards. In the opposing jaw the median series is very small, and the first Fig. 87. Jaws of Recent Myliobatis, lateral aspect. Fig. 88. .Jaws of Myliobatis aquila, Cuv. Anterior aspect. Mediterranean (after Agassiz). Recent : lateral row on each side large, with the outer lateral series diminishing. Common in the Chalk of Europe and North America, rarer in the Greensand. 44 PISCES CLASS I Promyliobaiis, Jaekel. A skeleton from the Upper Eocene of Monte Bolca, apparently showing pectoral fins less completely interrupted at side of head than in recent Myliobatis, otherwise resembling the latter. P. gazolae, Zigno sp. Myliobatis, Cuv. (Pastinaca, Gronow), (Figs. 87-90). The dental pavement of the jaws consists of seven antero-posterior rows of hex- angular flattened teeth closely pressed together. The lower dentition is longer and less arched than that of the upper jaw. In young examples all the teeth are similar in form and size, but during growth the f\ median series rapidly in- \, creases in width, and event- ually becomes from three to six times as broad as long, Myliobatis Fig toliapicus 81 >. An. Imperfect dentition. Middle'Bocene ; Bracklesham, while the shape of the lateral Sussex. . •11 series remains unchanged. The strongly developed root of each tooth is marked with parallel grooves on its lower and lateral faces. Numerous species represented by the dentition in the Tertiaries, and caudal spines also known. M. dixoni, Ag. ; M. sir kit us, Buckl. ; M. toliapicus, Ag., from English Eocene. M. pentoni, Sm. Woodw., the largest known species, from Eocene, Mokattam Hills, Cairo. M. magister, Leidy, the largest American species, known by complete dentition from the South Carolina Eocene. Rhinoptera, Midler (Zygobates, Ag. ; Mylorhina, Gill). Dentition of both jaws strongly arched antero-posteriorly. Teeth flattened and hexangular, in five to nine antero- posterior rows, and mostly broader than long, but diminish- ing in breadth outwards. Tertiary and Recent. R. daviesi, Sm. Woodw., from London Clay, Sheppey. Aetobatus, M. and H. (Goniobatis, Le Hon). Teeth very broad, in a single antero-posterior series. Tertiary and Recent ; distribution. Fig. i'O. Myliobatis serratus, H. v. Meyer. Caudal tin- spine. Oligocene ; Wein- heim, near Alzey. wide Order 5. HOLOCBPHALI. Chimaeras. Pterygoquadrate arcade completely and immovably fused with the cranium. Mandible provided with a very large dental plate on each side, meeting one or two pairs of denial plates in the upper jaw. Gill clefts covered by a fold of skin, so that there is only one external opening. Vertebral axis not distinctly segmented, and the not o chord surrounded by numerous partially calcified rings of cartilage. Paired fins with hvo or three short basal cartilages ; pelvic fins of male with appended claspers. The Holocephali occupy a unique position among the Selachii, on account of (1) the incompletely segmented character of the vertebral axis, in which the number of the cartilaginous rings considerably exceeds that, of the arches and processes; and (2) the fusion of the upper jaw with the skull. Their trunk sub-class i SELACHII 45 resembles that of the sharks, while the dentition is distinguished by the remark- ably peculiar form and structure of the few very large teeth or dental plates. Of the four surviving genera, Chimaera lives off' the European coasts, Japan, and the Cape of Good Hope ; Callorhynchus in the seas of the southern hemi- sphere ; Harriotta in the deep Atlantic off North America ; and Ehinochimaera in deep water off Japan. In all these genera the anterior dorsal fin is provided in front with a strong spine, which is supported by a broad plate of cartilage fixed to the vertebral column, and is united with this plate by a cartilage articulation. Besides the fin spine, the males of recent forms bear on the frontal region a spine which is rounded in front and covered with prickles, as well as smaller prickly spines in front of the pelvic fins. The long copulatory organs are also strengthened by thin calcified rods. The skin of the existing genera is naked, but in some extinct genera it is partly covered with shagreen granules and plates. A remarkable peculiarity of the Chimaeroids consists in the unusually conspicuous character of the mucous-canals, which traverse the skin of the head and form the very prominent lateral line of the trunk. These are surrounded by numerous, closely arranged, calcified rings of cartilage. The existing representatives of the Holocephali are only an insignificant remnant of a former much more extensively developed group of Selachians, which appears first in the Devonian, and is perhaps genetically connected with the Cochliodontidae. Family 1. Ptyctodontidae. Smith Woodward. 1 Known only by dental plates, which are laterally compressed, seem to form a single pair meeting at the symphysis of each jaw, and exhibit either feiu tritoral areas, or sharp catting edges. Devonian. Ptyctodus, Pander (Aulacosteus, Eichwald ; Rinodvs, Newb. and Worth.). Tritoral area composed of very hard, punctate, superimposed laminae, arranged obliquely to the functional surface. P. obliquus, Pander, from Middle Devonian, North Russia. P. molaris, East. ; Eifel Devonian. P. calceolus, Newb., and P. ferox, East. ; Middle and Upper Devonian, Wisconsin, Illinois, and Iowa. Bhynchodus, Newb. Dental plates with sharp cutting edges, and no well- differentiated tritors. North America, and the Eifel, Germany. Palaeomylus, Sm. Woodw. Robust teeth, with broad symphysial surface, and one punctate tritoral area, not laminated. North America. Family 2. Squaloraiidae. Smith Woodward. Trunk depressed and elongated, and head produced into a long, slender snout. Lower dentition comprising one pair, upper dentition two pairs of thin corrugated dental plates without definite tritors. Males with a prehensile spine on the snout. Dorsal Jin spine absent. Numerous conical or stellate dermal tubercles. Lower Jurassic. Squaloraja, Riley (Spinacorhiniis, Ag.). Tail tapering to a point. Rostral spine with expanded base, tapering to a point in front. Vertebral rings well calcified, consisting of several concentric lamellae. S. polyspondyla, Ag., known by nearly complete skeletons 0*45 in length, from the Lower Lias of Lyme Regis, Dorsetshire. 1 Eastman, C. R., Dentition of Devonian Ptyctodontidae (Amer. Xat. vol. XXXII.), 1898. 46 PISCES CLASS I Family 3. Myriacanthidae. Smith Woodward. Trunk elongated. Two upper pairs and one lower pair of thin dental plates, also a stout, median, incisor-like tooth at the symphysis of the mandible. Head with a few dermal plates. Males with a prehensile spine on the snout. Anterior dorsal Jin above the pectorals, with a long, straight, robust spine. Jurassic. Myriacanthus, Ag. (Prognathodus, Egerton ; Metopacanthus, Zittel). Rostrum with a terminal cutaneous flap. Anterior upper dental plate smaller than the posterior plate. Dorsal fin spine long and slender, somewhat laterally com- pressed, with a large internal cavity ; sides ornamented with small tubercles ; a series of large, thorn -shaped tubercles arranged along each edge of the flattened posterior face, passing into a single median row distally, and a single series of similar denticles on the anterior border. Rostral spine elongated and pointed, with expanded base. Dermal plates tuberculated. M. paradoxus, Ag., and M. granulatus, Ag., from Lower Lias of Lyme Regis. Chimaeropsis, Zittel (Fig. 91). Mandibular dental plates (md), slightly arched, with a large tritoral area ; the symphysial tooth (x) externally Chimaeropsis paradom, Zitt. Upper .Jurassic (Lithographic Stone); Eichstadt, Bavaria. i/-j uat. size. md, Mandibular tooth; p, Hinder upper tooth ; v, Anterior upper tooth in side view; v 1 , Same from lower side ; .<, Slender premandibular tooth. (inferiorly) convex, internally (superiorly) flat or concave. Anterior (v) and posterior (p) upper dental plates triangular, the former not smaller than the latter, and tapering in front, the latter tapering behind. Fin spine as in Myriacanthus. Body covered with small, conical, radiately grooved placoid scales. Upper Jurassic (Lithographic Stone) of Bavaria. Family 4. Chimaeridae. Chimaeras. 1 Trunk elongated, shark-like. Teeth forming t too pairs of robust dental plates in the upper jaiu, the foremost the smaller, both pairs thickened and closely apposed in the longitudinal mesial line of the mouth; lower dentition comprising a single pair of beak-shaped plates meeting at the symphysis; the plates usually with several trifors. Pectoral fins very large, fan-like, with simple, homy rays; anterior dorsal fin above the pectorals, with a large spine articulated to a cartilaginous base ; posterior dorsal 1 Newton, E. T., The Chimaeroid Fishes of the British Cretaceous Rocks (Mem. Geol Survey Mon. No. IV.), 1878. SUB-CLASS I SELACHII 47 fin hue, much extended. Skin naked, or with shagreen granules. Jurassic to Recent. Ischyodus, Egerton (Leptacanthus, Ag. ; Auluxacanthus, Sauvage; Chimaer- acanthus, Quenstedt), (Fig. 92). Lower dental plates rhomboidal, with a narrow symphysial facette ; upper part of outer face covered with a thick layer of dentine, and oral margin sharp ; four rough punctate tritors present. Posterior upper dental plates tri- angular, tapering in front, with four tritors ; anterior upper teeth square, antero -posteriorly compressed. Dorsal fin spine laterally compressed, smooth or longitudinally striated, with a double longitudinal series of denticles on the hinder face. Males with a short, arched head spine, bearing a cluster of denticles at the end. Nearly complete skeletons of /. avitus, Meyer sp. (Fig. 92), and /. quenstedti, from the Lithographic Stone of Bavaria. Detached teeth from the Bathonian (Stonesfield Slate) to the Upper Cretaceous of England, France, Germany, and Switzer- land ; also from Cretaceous of Amuri Bluff, New Zealand. Ganodus, Ag Dentition as in Ischyodus, but posterior upper dental plate deeply excavated behind, with a double longitudinal series of numer- ous small tritors. Bathonian (Stonesfield Slate), England. G. oweni, Ag., and other species. Fig. 93. Edaphodon sedgvncki, Ag. sp. Teeth, ' ■_• nat. size. Lower Chalk ; Lewes. ni'l, Left mandibular tooth, inner aspect; p, Left hinder upper tooth, oral aspect; r, Left anterior upper tooth, inner aspeel : a, Tritors; sym, Sym- physial border (after E. T. Newton). Ischyodus avitus, H. v. Meyer. Almost complete skeleton, !/ 2 nat. size. Upper Jurassic ( Lithographic Stone) ; Eichstadt (after II. \. Meyer). Pachymylus, Brachymylus, Sm. Woodw. Upper Jurassic ; England. 48 PISCES CLASS I Edaphodon, Buckland (Passalodon, Buckl. ; Eumylodus, Mylognathus, Leidy ; Dipristis, Marsh; Leptomylus, Cope), (Fig. 93). Lower dental plates with a broad symphysial facette ; posterior upper dental plates tapering in front, truncated behind, and with three tritors. Cretaceous, Eocene, and Oligocene of Europe and North America. Elasmodectes, Newton (Elasmognathus, Newton, non Gill). Mandibular teeth laterally compressed and trenchant, with a series of small tritors along the oral border. E. willetti, Newton, from Lower Chalk, Kent. Amylodon, Storms. Lower Miocene (Rupelian) ; Belgium. Elasmodus, Egerton. Upper Cretaceous of Belgium ; Eocene of England and Prussia. Dental plates of the existing genus Callorhynchus, Gronow, have been identified from the Cretaceous of Amuri Bluff, New Zealand ; of the existing genus Chimaera, Linn., from the Upper Tertiary of Europe and Java. rvtf-O Fig. 94. Onchus tenuistriatiis Pin-spine, nat. size Silurian ; Ludlow, En Ag. Upper land. I '! Ichthyodorulites. Fossil fin spines consisting of dentine or vasodentine, and thus presumably referable to the Selachii, are frequently found isolated especially in the Palaeozoic formations, and can only be in part assigned to definite genera. These are therefore described under provisional generic names. Most of them are bilaterally symmetrical, and may be regarded as median dorsal spines ; but several are distinctly rights and lefts, and belong either to the paired fins, as in Acanthodidae, or to the side of the head, as in Menaspis among Cochliodontidae. In the unsym- metrical spines, the base is, as a rule, abruptly truncated ; in the bilaterally- symmetrical dorsal spines, on the other hand, it is usually elongated and tapers to the proximal end. Among the Ichthyodorulites not yet referable with certainty to definite genera or families, the following may be enumerated . — (a) Slender, bilaterally-symmetrical spines, with a smooth base sharply separated from the exserted portion ; internal cavity open posteriorly towards the base. Probably for the most part referable to the Cestraciontidae. Onchus, Ag. (Fig. 94) ; Upper Silurian and Devonian, Europe and eastern North America. Ctenacantkus, Ag. (Fig. 95), possibly the fin spines of Orodus ; Lower Carboniferous, Europe and North America. Homacanthus, Ag. ; Devonian and Lower Carboni- ferous. Acondylacanthus, St. J. and Worth. ; Asteroptychius, M'Coy ; Lispacanthus, Davis ; Geisacanthus, St. J. and Worth.; Lower Carboniferous. Lepracanthus, Owen ; British Coal Measures ■; Fig. 95. Ctmaamthits denticu- latus, M'Coy. 1/2 """at. size. Carboniferous Limestone ; Monaduff. Ireland (after M'Coy). Wodnika. SUB-CLASS I SELACHI1 49 Wodnika stria Riechelsdorf, Hesse. Fig. 96. Miinst. Enlarged. Kupferschiefer ; A, Fin-spine. B, Shagreen granules. Miinster; Permian (Kupferschiefer of Germany), (Fig. 96). Nemacanthus, Ag. ; Bhaetic and Lower Jurassic. (b) Slender, bilaterally - sym- metrical spines, with little or no smooth, inserted portion, and in- ternal cavity only open at the proximal end. Gnathaca athus, Davis; Lower Carboniferous, Armagh, Ireland. Pristacanthus, Ag. ; Bathonian, Oxfordshire and Normandy. (c) Bight and left paired spines, most probably connected with fins. Machaeracanthus, Newb. (Fig. 97) ; Meter acanthus, Newb. ; Hapla- canthus, Ag. De- vonian ; Europe and North America. Gyro- cant h us, A g. Lower Devonian (Canada) to Upper Carboniferous (Europe and North America). (d) Paired spines, usually with a broad, truncated base, a large internal cavity and the outer face tuberculated. Probably lateral head spines, as in Menaspis among Cochliodontidae. Ora- canthus, Ag. (Platyacanthus, M'Coy; Pnigeacanthus, St. J. and Worth.; Phodt ra- canthus, Davis.) Carboniferous of Europe and North America (spines already observed on either side of head in one example of 0. armigerus, Traquair, from Calciferous Sandstones of Eskdale, Dumfries). Physonemus, M'Coy (Xystra- canthus, Leidy ; Drepanacanthus, Newb.); Erismacanthus, M'Coy; Gampsacanthus, St. J. and Worth. (Fig. 98); Lecra- canthus, St. J. and Worth. ; Dipria- canthus, M'Coy, etc. Lower Carboni- ferous. (e) Spines of entirely doubtful posi- tion. Cynopodius, Traquair. Lower Missouri (after st."jonn Carboniferous ; Scotland. Euctenius, Traquair. Coal Measures ; Scotland, England, and Ohio, U.S.A. Stethacanthus, Newb. Upper Devonian and Lower Carboniferous ; Ohio, Illinois, and Iowa. Fig. '.'7. Mocha* racanth us major Newberry. Middle De vonian ; Sandusky, Ohio 1 -j nat. size (after New 1 terry). Gampsacanthus typus, St. John and Worthen. Carboniferous Lime- stone ; St. Louis, VOL. II E 50 PISCES class i Sub-Class 2. 0STRAC0DERMI. Cope. Early Palaeozoic fishes with persistent notochord, and endoskeleton not calcified. Mandible and arches for paired fins apparently absent. Exoskeleton well developed, the head and anterior portion of the trunk usually covered with plates. Mouth without hard parts. The Ostracoderms form one of the most characteristic groups of the early Palaeozoic fish-fauna ; but their true systematic position is still uncertain. Their remains were formerly compared with the armour of reptiles such as .tortoises, and also with crabs and water-beetles ; while more lately they have even been supposed to exhibit resemblances to Arachnids. They were first recognised as fishes by Agassiz, and referred by him to the Ganoidei. Unless appearances in the fossils are deceptive, they are distinguished from all typical fishes, and agree with the Cyclostomi in the lack of a lower jaw and of arches for paired limbs ; but there seems to be evidence of paired nasal openings in Pterichihys and Bothriolepis. Four orders of Ostracophores may be recognised as follows : — Heterostraci, Anaspida, Aspidocephali, and Antiarcha. In the first, the exoskeleton sometimes consists of placoid tubercles of dentine, as in sharks ; in the second tin- tubercles on the head region are never fused. In the more typical Hetero- straci, as also in the Aspidocephali and Antiarcha, this primitive armour is modified so that the head and anterior abdominal region become invested with dermal plates, which are usually as well developed as in modern sturgeons and certain bony fishes (Siluridae). The sub-class is restricted to the Upper Silurian and Devonian. Order 1. HETEROSTRACI. Ray Lankester. 1 Exoskeleton consisting of shagreen, plates, or scales, without bone cells ; each fully formed plate mm prising three superimposed layers — an inner "nacreous" layer of lamellae, a re I 'a ti rely thick middle zone tvith numerous vacuities, and an outer hard layer of vaso-dentiue. Dorsal shield, when present, of few pieces, and orbits wide apart, laterally placed. No paired appendages. Family 1. Coelolepidae. Pander. Head and trunk relatively large and depressed, completely covered with placoid tubercles of dentine, scarcely if at all fused into groups: the small, slender caudal region sharply constricted from the head region and distinctly heterocercal . Upper Silurian and Lower Devonian. The dermal tubercles of genera of this family have long been known from i lie Upper Silurian of England and the Isle of Oesel in the Baltic Sea; but until the discovery of complete specimens in the Upper Silurian of Lanark- 1 Alth ) A. run, Ueber Pteraspis, Cyatkasjns, mid Scaphaspis (Beitr. Palaeont. Oesterr. - Ungarns, vol. II.), 188Q.— Huxley, T. H., On Cephalaspis and Pteraspis (Quart. Journ. Geo!. Soc. vols. XII., XIV., XVII.), 1856, 1S58, 1861.— Kner, R., Ueber Cephalasjns lloydii und lewisii (Haidinger's Naturw. Abhandl. vol. I.), 1847. — Kunth, A., Ueber Pteraspis (Zeitschr. deutsch. geol. Ges. vol. XXIV.), 1872. — Lankester, Ray, and Powrie, J., A Monograph of the Fishes of the Old Red Sandstone. I. Cephalaspidae (Mon. Palaeont. Soc), 1868. — Roemer, Ferd., Ueber Palae<>- teuthis dtmensis (Palaeontogr. vol. IV.), 1856. — Traqvair, R. H., Report on Fossil Fishes, etc. (Trans. Uov. Soc. Edinb. vol. XXXIX. Nos. 21, 32), 1899. SUB-CLASS II OSTRACODERMI 51 Cephaloptems, quadrangular, Fig. 99. TTielodus parvidens, Ag. Dermal foibercles, nat. size (above) and enlarged. [Tpper Silurian (Ludlow Bone Bed); Ludlow. Passage shire, they were commonly supposed to belong to sharks. The latter discovery is considered by Traquair to indicate some close relationship between the Ostracophores and the primitive Selachii. Thelodus, Ag. (Coelolepis, Pachylepis, Thelolepis, Pander Powrie; Turinia, Traq.), (Fig. 99). Dermal tubercles small and nearly uniform. A small dorsal fin near base of heterocercal tail. No enlarged ridge scales. T. parvidens, Ag. ; detached tubercles in Ludlow Bonebed and Oesel Limestone. T. scoticus, Traq. ; complete skeletons in Upper Ludlow, Logan Water, Lanarkshire. T. pagei, Powrie sp. ; complete skeleton, Lower Old Red Sand stone, Turin Hill, Forfarshire. LanarMa, Traq. Dermal tubercles are small, pointed hollow spines, not of uniform size. L. horrida, Traq., and other species represented by skeletons in the Upper Silurian Beds of Birkenhead Burn and Seggieholm, Lanarkshire. Family 2. Psammosteidae. Traquair. Dermal armour of head region more or less completely fused into large plates. External layer of each dermal plate forming a tubercular ornament. Dermal sense organs not penetrating the tissue of the armour. Devonian. Psammosteus, Ag. (Placosteus, Ag. ; Pscmmolepis, Ag.). External ornament of very closely arranged, rounded, or elongated tubercles which are usually crimped round the margin. Orbit probably enclosed in the shield. Paired spines (of un- certain position) broad and tri- angular, with a large internal cavity and short base of insertion. Large ridge scutes on the tail, ornamented as the body shield and paired spines. P. maeandrinus, Ag.,and P. paradoxus, Ag., from Upper Devonian, Russia. P. taylori, Traq., from Upper Old Red Sandstone, Elgin. Other species from the Lower Old Red Sandstone of west of England, and from Upper Devonian, Spitzbergen. Drepanaspis, Schliiter (Fig. 100). Head region covered with one large median plate, two postero - lateral plates, two rostral plates, and intervening small polygonal plates. Tail as in Psammosteus. D. gnu ut ndenensis, Schliit,, from Lower Devonian, Gemunden, Eifel. Fig. loo Drepanaspis gemuendenensis, Schliiter. Restored out- line of ventral aspect, surface ornament omitted. Lower Devonian; Gemunden, Eifel. m.v, Median ventral plate; p.l, Postero-lateral plates; p.v.l, Postero-ventro-lateral plates; r, Rostral plates ; x, Orbits. 1/4 (after Traquair). 52 PISCES CLASS I Family 3. Pteraspidae. Smith Woodward. Dermal armour of head region completely fused into large plates. External layer of each dermal plate forming an ornament of very fine, concentric, closely arranged ridges, parallel with the outer margin ; middle layer with large polygonal cancellae. Dermal sense organs well developed, arranged in canals traversing the middle layer of the shield and opening by a double series of pores ex- ternally. Ventral shield simple. Tail presumably heterocercal, and scales of caudal region, when preserved, numerous and rhomboidal. Upper Silurian and Lower Devonian. Three genera of this family are distinguished according to the com- plexity of the dorsal shield. The simple ventral shield, similar in each form, was originally mistaken for dorsal armour, and named Scapliaspis by Lankester. I'ic. 101 Pte raspis, Kner "A. /;. Ptt raspis rostrata, Ag. sp. Lower Old Red Sandstone (Cornstones) ; (PalaeoteiltMs, .Al'chaeo- Heretbrdshire. .4, Dorsal shield, 1/2 na t- size, restored. B, Ventral jdiield f^+j,-,, t? (Scaphaspis lloydi, Ag. sp.), 2/3 nat. size (after Ray Lankester). C, Dorsal teUttllS, £. xCoemerj, and ventral shields of Pteraspis, lateral aspect, restored from a specimen /f ip-g 101-103) Doi'- found in Galicia (after Alth). *" it-i-i-ii sal shield arrowhead- shaped, consisting of seven separately calcified plates — a large central disc ; ■~— c Fig. 102. Pteraspis rostrata, Ag. sp. Piece of shield, much magnified, a, Upper, b, Middle, and c, Lower layer (after Ray Lankester). Fig. 103. Pteraspis rostrata, Ag. sp. Vertical section of head shield parallel with a longitudinal rib, highly mag- nified (after Ray Lankester). a triangular rostral plate in front ; a median spine behind ; a pair of orbital plates, completely enclosing the orbit on either side, and partially inserted between the rostrum and central disc ; and a pair of lateral cornua, each SUB-CLASS II OSTKACODERMI 53 pierced by a large, apparently branchial foramen. P. rostrata, Ag. sp. (Fig. 101), and other species from the Lower Old Red Sandstone of England, Scotland, Rhenish Prussia, and Galicia ; also from the Upper Silurian of Galicia, and probably from the Lower Devonian of Spitzbergen. Palaeaspis, Claypole (Holaspis, Lank, non Gray). Dorsal shield apparently simple, without posterior spine; orbits merely forming notches. P. americana, Clay., from Upper Silurian (Onondaga Group), Pennsylvania. P. sericea, Lank, sp., from Lower Old Red Sandstone, Monmouthshire. Cyathaspis, Lank. (Diplaspis, Matthew). Dorsal shield consisting of a large central disc ; two long and slender lateral cornua, which are notched anteriorly by the orbits and pierced further back by the supposed branchial foramen, and a short and broad rostral plate. C. ha nisi, Huxley and Salter sp., from Upper Silurian (Ludlow Bone-bed and Passage Beds) of Herefordshire. C. schmidti, Geinitz, from Wenlock Limestone of Isle of Gotland. Other species from corresponding formations in Germany, Galicia, and New Brunswick. The so-called Scaphaspis ludensis, Salter sp., from Lower Ludlow, Leintwardine, probably belongs to this genus. Order 2. ANASPIDA. Traquair. 1 Tubercles only on the head region, not fused into plates ; the calcifications probably in part with bone cells. No paired appendages. Family 1. Birkeniidae. Traquair. External ornament, when present, tubercular. Branchial openings a series of small perforations laterally placed. One small dorsal fin ; tail heterocercal. Upper Silurian. Birkenia, Traq. (Fig. 104). Trunk irregularly covered with deepened Fig. 104. Birkenia elegans, Traq. Restored outline in side view, about nat. size. Upper Silurian ; Lanarkshire (after Traquair). d, Dorsal fin. scales ; a series of large scutes along the ventral border. © © B. elegans, Traq. Upper Silurian ; Lanarkshire. Lasaniuspi licus, Traq. Restored outline, about nat. size. Upper Silurian ; Lanarkshire, r, Postcephalic rods; r', Chain of ossicles; v.s, Ventral scutes (after Traquair). Lasanius, Traq. (Fig. 105). Trunk naked, except immediately behind the 1 Traquair, R. H., Report on Fossil Fishes collected by the Geological Survey of Scotland in the Silurian Rocks of the south of Scotland (Trans. Roy. Soc. Eclinb. vol. XXXIX., with 5 pis.), 1899. 54 PISCES CLASS I head, where rudiments occur ; a series of large scutes along the ventral border. L. problematicus, Traq. Upper Silurian , Lanarkshire. Family 2. Euphaneropidae. Smith Woodward. As Birkeniidae, but no series of branchial openings. Upper Devonian. Euphanerops, Sm. Woodw. E. longaevus, Woodw., the type species, is the only known Ostracophore which displays traces of the axial skeleton of the trunk. Upper Devonian ; Canada. Order 3. ASPIDOCBPHALI. Brandt. 1 (Osteostraci, Kay Lankester.) Exoskeleton consisting of calcifications, partly with bone cells ; each plate in the head region comprising three superposed layers — an inner laminated layer tvith spindle-shaped bone cells; a relatively thick middle layer of polygonal cancellae which may be more or less solid though with a coarse reticulation of large vascular canals; also an outer hard layer of vaso-dentine. Orbits close together. No paired appendages. Family 1. Ateleaspidae. Traquair. Head shield rounded or tapering in front, abruptly truncated behind, consisting of loose plates. Body covered with quadrangular scales which are deepened on the flank. Tail heterocercal. Upper Silurian. Ateleaspis, Traq., from the Upper Silurian Passage Beds of Seggieholm, Lanarkshire. The tubercles of the head region are fused together into small plates. The genus may be a link between the Heterostraci and Osteostraci, but the microscopical structure of the armour agrees with that of the latter. Family 2. Cephalaspidae. Agassiz. Bead shield rounded or tapering in front, abruptly triturated behind ; interorbital piece firmly fixed ; an ornament of rounded or stellate tubercles. Dermal sense organs leaving no impressions on the exoskeleton. Body covered with quadrangular scales, which are deepened on the flank. One small dorsal Jin ; tail heterocercal. Upper Silurian to Upper Devonian. Cephalaspis, Ag. (Eucephalaspis, Hemicydaspis, Zenaspis, R. Lank.), (Figs. Fig. 100. Cephalaspis lyelli, Ag. Lower Old Red Sandstone ; Arbroath, Scotland. 1/2 nat. size (after Ray Lankester). 106, 107). Postero-lateral angles of shield more or less produced into pointed cornua, external to a small flexible flap on each side, which is stiffened by 1 Huxley, T. H., On Cephalaspis and Pteraspis (Quar. Journ. Geol. Soc. vols. XII., XIV., XVII.), 1856, 1858, 1861.— Lankester, E. R., The Cephalaspidae (Monogr. Palaeont. Soc), 1867-69.— Schmidt, Friedr., Verhandl. k. russ. mineral. Ges. 1873 and 1886; and Bull. Acad. Imp. Sci. St. Petersb. 1894.— Rohon, J. V., Die obersilurischen Fische von Oesel I. (Mem. Acad. Imp. Sci. St. Petersb., ser. 7, vol. XXXVTII.). 1892 : also Bull. Acad. Imp. 1893. SUB-CLASS II OSTRACODERMI 55 bony plates, and seems to represent an operculum. Body triangular in trans- verse section, the flanks covered with three longitudinal series of deepened scales, the middle series deepest. Ventral scales small. Dorsal fin triangular, at the base of the heterocercal tail ; membrane of dorsal and anal fins stiffened with very small calcifications which are arranged in parallel rows simulating ravs. C. lyelli, Ag. (Fig. 106), from Lower Old Red Sandstone of Scotland and west of England. C. magnified, Traq., the largest known species, with shield measuring - 22 m. across, from Caithness Flagstones. Other species from Upper Silurian and Lower Devonian of Scotland,. England, and Canada. One species (C. loMceps, Traq.), from Upper Devonian, Scaumenac Bay, Canada. Eukeraspis, Lank. (Sclerodus, Plectrodus, Ag.). As above, but posterior cornua excessively elongated, and a row of twelve large " marginal cells " around the rim in front. The detached denticulated cornua were originally mistaken for jaws. E. pustulifera, Ag. sp., from Upper Silurian, Herefordshire. Thyestes, Eichw. (Auchenaspis, Egerton). Head shield as in Cephalaspis, but three or four series of dorso-lateral scales fused into a continuous plate immediately behind it. Body depressed, ovoid in transverse section. Known species very small. T. verrucosus, Eichw., from Upper Silurian, Isle of Oesel. So-called Auchenaspis from Upper Silurian and Lower Old Red Sandstone Passage Beds of Herefordshire. Fig. 107. Head shield of Cephalaspis lyelli, Ag. Lower Old Red Sandstone ; Herefordshire (after Lan- k ester). l/ 2 . Family 3. Tremataspidae. Smith Woodward. Head shield rounded or tapering in front, fused with the dorsal body-shield, which is truncated behind; interorbital piece not fixed. Upper Silurian and Lower Devonian. Tremataspis, Schmidt. Dorsal shield rounded in front, gently arched, without cornua ; ventral shield simple. External surface covered with punctate ganoine, the punctations often arranged in reticulating lines ; superficial tuberculations almost or entirely absent. Two pairs of large openings laterally placed in the anterior half of the dorsal shield arc in- terpreted by Smith Woodward as occurring in the roof of the branchial chamber, covered over during life but ensuring flexibility. Ventral aspect immediately behind the position of the mouth covered with a number of symmetrically arranged polygonal plates, between which and the great ventral plate of the trunk is a transverse series of nine small openings on each side, probably of branchial nature. Tail covered with rhombic and polygonal scales, which have been named Dasylepis, Dictyolepis, Melittomalepis, and Stigmolepis by Pander. T. schrenki, Pander sp., and other species in the Upper Silurian, Isle of Oesel, Baltic Sea. Did ymaspis, Lankester. D. grindrodi, Lank., from Lower Old stone, Ledburv, Herefordshire. Red Sand- 56 PISCES CLASS I Order 4. ANTIARCHA. Cope. 1 Dermal armour fused info large plates on the head and abdominal region. Exo- skeleton consisting of calcifications with bone corpuscles, and invested with a more or less continuous layer of ganoine. Dermal sense organs occupying open grooves on the exoskeleton. Dorsal and ventral shields consisting of several symmetrically arranged pieces, and the head articulated with the trunk. Orbits close together. A pair of paddle-like pectoral appendages, invested in dermal plates, articulated with the anterior ventro-lateral plates of the trunk. Median fins not continuous. The bony plates of the Antiarcha consist of three layers with numerous bone cells, the middle layer traversed by large canals and lacunae, while the outer and inner layers exhibit a more compact texture. Family 1. Asterolepidae. Traquair. Exoskeleton robust and tuber culated. Dorsal and ventral shields of trunk firmly united by the lateral plates. Interorbital piece not fixed. A pair of paddle-lih appendages, completely encased in dermal plates, movably articulated by a complex joint with the anterior ventro-lateral plates of the trunk. Tail heterocercal, and one small dorsal fin. Devonian. Plerichthys, Ag. (Pterichthyodes, Bleeker), (Figs. 108, 109). From 3 to 20 Fig. 108. Pterichthys milleri, Ag. Restoration from above (A), below (JJ), and in side view (C). Lower Old Red Sand- stone ; Scotland, ap, Pectoral appendages ; j, Articulation ; op, Operculum ; orb, Orbit (after Traquair). cm. in length, with a small head, which is rounded in front, a broad and deep trunk flattened below, and a scaly tail. The upper surface of the head is 1 Pander, C. If., Die Placodermen des devonischen Systems. St. Petersburg. 1857. — Traquair. R. H., Ann. Mag. Nat. Hist. ser. 6, vol. II. 1888 ; and Mon. Palaeont. Soc, 1S94. SUB-CLASS II OSTRACODEEMI covered with four pairs of lateral plates and four unpaired median plates, which are united by straight sutures. On the lower surface the cleft for the mouth is bounded in front by a pair of transversely elongated plates, which are sometimes supposed to represent the upper jaw. Behind the cleft a pair of smaller plates occurs fixed to the front of the abdominal shield. The trunk is armoured above by two large median and two pairs of lateral plates ; on its ventral surface four large ventrolaterals surround a small rhombic ventro - median element. The ventro- laterals are sharply bent upwards and outwards near their lateral border to take part in covering the flank. Both the head ,plates and the dorso-lateral plates of the trunk are traversed by sensory grooves, those of the head being united by two parallel com- missures. The two hinder lateral plates of the head and the adjoin- ing body plates have bevelled edges, so that the former overlap the latter. The anterior median dorsal plate of the trunk somewhat overlaps the lateral plates, and is overlapped behind by the border both of the posterior dorso-laterals and of the posterior median dorsal plate. The orbits occur at the two ends of a transverse cleft on the upper sur- face of the head, and are separate^! by a quadrangular median plate (os dubium or os pineale), which exhibits a small deep pit On its inner face. £ a ™ rie ' Scotland. A, Specimen in nodule, 1/2 lia t. size _,. x x B, Scale enlarged (after Egerton). Ine two anterior ventro - lateral plates of the trunk are provided in front with an articular hollow on each side, in which are fixed the armoured paddle-shaped pectoral appendages. The latter do not reach the hinder end of the body shield, and exhibit one trans- verse articulation (j) at about their middle. The tail is covered with thin, rounded, or six-sided, overlapping scales. The single dorsal fin is small. The tail is heterocercal, with large fulcral scales on its upper border, and the fin membrane confined to the lower lobe. P. milleri, Ag., and other species represented by complete but usually ill-preserved examples in the Lower Old Red Sandstone of Scotland. Fragments in the Middle Devonian of the Eifel. Asterolepis, Eichw. (Narcodes, Odontacanthus, Ag.). As Pterichthys, but often larger, and the anterior median dorsal plate overlaps both the anterior dorso- laterals and the posterior dorso-lateral plates. Chiefly represented by detached plates in the Devonian of N.-W. Russia and in the Upper Old Red Sandstone of Scotland. More doubtful fragments from the Devonian of Bohemia, the Eifel, East Greenland, and Australia. Fig. 109 Pterichthys milleri, Ag. Lower Old Red Sandstone : PISCES CLASS I Jlicrobrachius, Traquair. M. dichi, Traquair, from Lower Old Red Sandstone, Caithness and Orkney. Bothriolepis, Eichw. (Pamphractus, Placofhora.v, Eomothorax, Glyptosteus, Ag.). Armour nearly as in Pterichthys, but the pectoral appendages reaching back- wards beyond the body shield, and the hinder mucous canal commissure on the head V-shaped. Tail unknown, probably not scaly. An Upper Devonian genus, known from N.-W. Russia, Scotland, England, Canada, and Penn- sylvania. Remarkably fine examples of the armour of B. canadensis, Whit- eaves, 0*20 m. in length, from Scaumenac Bay, Province of Quebec, Canada. iCeraspis, Schluter; Belemnacanthus, Eastm. Middle Devonian ; Eifel. IXCERTAE SEDIS. Macropetalichthi/s, Norwood and Owen. Plates of cranial shield fused together in adult; orbits completely enclosed in the shield; sensory canals forming large tubular excavations in the bone, opening at the external surface by a continuous narrow slit or a series of pores. Jaws and other parts of the skeleton unknown. Middle Devonian (Corniferous Limestone) ; U.S.A. Also Upper and Lower Devonian of Eifel. Asterosteus. Xewb. Known onlv bv the flattened and elongated cranial shield, which has the constituent elements fused in the adult. Orbits placed far forwards and forming broad notches. Corniferous Limestone ; Ohio. Sub-Class 3. ARTHRODIRA. Smith Woodward. Early Palaeozoic fishes with persistent notochord, and endosJceleton superficially calcified. Head and trunk armoured with symmetrically arranged bony plates, somt of which are traversed by sensory grooves ; head shield movably articulated by a pair of ginglymoid joints with the body shield. Paired fins rudimentary or absent. The Coccostean fishes were originally grouped by M'Coy with Asterolepis and Pterichthys in the " family Placodermi," and they are included by Pander in his " Placodermen." The resemblance between their jaws and those of the existing Dipnoi was pointed out by Newberry and Traquair ; and they were provisionally regarded as an order of Dipnoi by Smith Woodward. Dean elevates them to the rank of an independent class, removing them from Pisces on the ground that their jaw elements are merely dermal ossifications, and are not articulated with the skull. Family 1. Coccosteidae. Smith Woodward. 1 Head shield comprising thret pairs of lateral plates, cue large median occipital plate, and two symmetrical pairs of plates in front of the latter, the foremost pair surrounding one or two small median plates. Orbits lateral ; nasal openings small and far forwards ; dental plates movable, toothless, or provided with cusps of dentine. Trunk with a large median dorsal plate often bearing a longitudinal median keel on its under surface; also two pairs of lateral plates, the anterior with a pair of articular 1 Traquair, It. H.. On the Structure of Coccostevs decipii -. A.g. (Ami. Mag. Xat. Hi>t. ser. 6, vol. V. p. 125), 1S90.— Dean, B.. Palaeontological Notes (Mem. N. Y. Acad. Sei. vol. II. pt. 1901. — /. , . 0. A'.. Some new points in Diniehthyid Osteology (Ainer. Nat. vol. XXXII. p. 747), 1898. SUB-CLASS III ARTHRODIKA 59 processes for anion with the head shield. Ventral body armowr comprising two or three pairs of lateral plates and two small unpaired median plates. All external I'hites more or less tuberculated. Dorsal fin small ; anal fin unknown; tail diphy- cercal or heterocercal. Devonian. Coccosteus, Ag. (Liognathus, Newb.), (Figs. 110, 111). Head and trunk broad, the dermal plates covered with stellate tubercles. Cranial plates uni by sutures, not fused. Orbit forming a notch in the anterior part of the lateral border of the shield ; a bony sclerotic ring present. Besides the "maxilla" and "premaxilla," one or two inner pairs of dentigerous bones also osteus decipv Fig. 110. Ag. Left antero-dorso-lateral plate of trunk, inner (A), anil outer i Lower Old Red Sandstone ; Scotland. present in the upper jaw. In front of the ventral body shield occur a pair of transversely elongated slender plates, perhaps representing the pectoral arch : a small pectoral spine, but never any traces of pectoral fins observed. Ribs absent. Dorsal fin short-based. Tail destitute of scales. Nearly com- plete but imperfectly preserved skeletons of C. decipiens, Ag. (Figs. 110, 111), occur in the Lower Old Red Sandstone of Scotland. Fragments of other Fig. 111. Coccosteus decipiens, Ag. Restoration, 1/2- Lower Old Red Sandstone : Scotland (after Smith Woodward). species in the Upper Devonian of England, Ireland, Germany, Russia, and Canada. Also from Corniferous Limestone (Middle Devonian), Ohio, I .S.A. Brachydirus. v. Koenen. Considered bv von Koenen to differ from Cocco- stem in the presence of a pair of hollow spines which perhaps represent pectoral fins. Upper Devonian ; Bicken, Xassau. Phlyctaenaspis, Traquair. Lower Devonian; Canada, west of England, and Russian Poland. Acanthaspis, Xewb. Lower and Middle Devonian ; U.S.A. Chelyophorus, Ag. Upper Devonian ; Russia. Dinichthys, Xewberry (Fig. 112). Very large, the head sometimes measuring 1 m. in length and 0'7 m. in breadth. Median occipital plate sub- triangular with prominent median process behind ; lateral occipital plates with very deep articular sockets for the reception of the process on the antero-dorso- lateral plates of the body shield. Orbit forming a notch as in Coccostmis. Pre- 60 PISCES CLASS I maxillae and synrphysial end of mandibular bones with a pair of stout cusps or beaks, and the trenchant margin behind these sometimes toothed. Median dorsal plate very thick, often over 0"6 m. long and broad. Antero-dorso-lateral Pig. 112. Dinichthys Jierzeri, Newberry. Diagrammatic front view of upper and lower jaws, 1 fe. Upper Devonian (Huron Shales) ; Delaware, Ohio (after Newberry). plate overlapped by the large " clavicular." Several species in the Middle and Upper Devonian of Iowa, Wisconsin, Ohio, New York, and Canada ; others in the Devonian of the Eifel, Bohemia, and Russia. Titanichthys, Xewb. Cranial shield very large, thin and flattened, arrangement of plates closely similar to that of Din- ichthys. Jaw elements much reduced, edentulous, probably sheathed in horn. Dorso- median without an inferior longitudinal keel, deeply emarginate in front. Antero- and postero-dorso-laterals fused, articulated to the cranial shield by a long hinge, and over- lapped by the large claviculars. T. agassizi, N., has a horizontal expanse of 1*9 m. across head- shield and claviculars. Cleveland Shale (Upper Devonian) ; Ohio. Homosteus, Asmuss. (Fig. 113). Very large fishes, broad and de- pressed. Orbits completely en- closed in the head shield ; jaws slender and toothless. Median Fig. 113. Homosteus milli ri, Traq. Cranial and dorsal shield, i/e lia t- size. Lower Old Red Sandstone; Caithness. A, B, C, Un- determined bones ; adl, Anterior dorsolateral ; etc, Ethmoid; c, Central ; eo, External occipital ; m, Marginal ; md, Median occipital plate ailterO-pOSteriorlv dorsal ; mo, Median occipital ; o, Orbit ; pdi, Posterior dorso- , . -, -,. -iii r lateral; po, Preorbital; pto, Postorbital. Pineal plate elongated; median dorsal plate 01 behind " ethmoid " or rostral. The double lines indicate the 4.U +r , m i. l-M-norlm- +Vmn lnno- 77 course of the sensory grooves (after Traquair). tneLiUiiK uioduei uiiciii iun^,. xx. millerij Traq., from Lower Old Eed Sandstone, Caithness and Orkney. Other species in Upper Devonian of Livonia. Heterosteus, Asmuss. Nearly resembling Homosteus, but larger, and anterior dorso-lateral body plates with an enormous anteriorly directed process which SUB-CLASS IV DIPNOI 61 clasps the head shield on each side. H. asmussi, Ag. sp., common in Upper Devonian of Livonia, but known only by the massive detached plates. Aspidichthys, Glyptaspis, Trachosteus, Newberry; Anomalichthys, v. Koenen ; Asteroplax, Sm. Woodw. Devonian. Mylostoma, Diplognathus, Newberry; Selenosteus, Stenosteus, Dean. Upper Devonian (Cleveland Shale) ; Ohio. Most of the genera enumerated on this and the preceding page are regarded by Dean and others as types of distinct families. Sub-Class 4. DIPNOI, Mtiller. 1 Lung-fishes. Skeleton partially ossified, with numerous well-developed membrane bones. Pterygo- quadrate arcade completely and immovably fused with the cranium; gill clefts feebly separated, opening into a cavity covered with a bony operculum. Paired fins paddle- like, with a long, segmented cartilaginous axis (archipterygium of Gegenbaur) ; tail diphycercal or heterocercal. In the living forms — optic nerves not decussating, but forming a chiasma, bulbus arteriosus of the heart with numerous valves, intestine with a spired valve, and air-bladder lung-like. The internal skeleton of the Dipnoi is chiefly cartilaginous, but the upper and lower vertebral arches, the ribs and fin-supports, all exhibit some tendency towards ossification. The Dipnoi differ so much from all fishes, in the modification of the air- bladder into a single or double elongated sac with numerous cellular spaces, which serves as 'a lung and is connected by a short tube with the anterior wall of the gullet ; moreover, in the peculiar characters in the structure of the heart, in the presence of internal narial openings, and in the possession of the faculty of existing for a considerable period out of water, that they have often been regarded as fish-like Amphibia or scaly Sirens. The discovery of the "Barramunda" (Ceratodus forsteri) in the rivers of Queensland confirmed the idea of their relationship to the Palaeozoic Crossopterygians previously suggested by Huxley. Nevertheless, they are distinguished from these and from all other Ganoids and Teleosteans by the autostylic arrangement of the jaws. They are divided into the two orders of Ctenodipterini and Sirenoidei. Order 1. CTENODIPTERINI. Pander. Cranial roof bones snail and numerous. Pays of median fins very fine, much more numerous than their supports, which are directly apposed to the vertebral arches. Family 1. Uronemidae. Traquair. Upper dentition comprising a cluster of small, blunt, conical denticles on the palatine bones; lower dentition of similar denticles on the splenial. Median fins continuous and tail diphycercal. Lower Carboniferous to Lower Permian. 1 Gtuither, A., Description of Ceratodus (Phil. Trans, vol. CLXI.), 1871-72.— Huxley, T. 1L, Proc. Zool. Soc. 1876, p. 24. — Miall, L. C, Monograph of the Sirenoid and Crossopterygian Ganoids (Palaeont. Soc), 1878. — Pander, C. H., Ueber die Ctenodipterinen, etc., des devonisehen Systems. St. Petersburg, 1858. — Traquair, II. H., On the genera Dipterus, Palaedaphus, Holodus, and Gheirodus (Ann. Mag. Xat. Hist. ser. 4, vol. XVII.), 1878 (also ibid, ser. 5, vol. II.).— Teller, F., Ueber Ceratodus sturi (Abh. k.k. geol. Reichsanst. Wien. vol. XV.), 1891. — Zittel, K. A. >■<,,,. Ueber Ceratodus (Sitznngsb. k. bay. Akad. YYiss.. math.-phys. CI.), 1886. 62 PISCES CLASS I Uronemus, Ag. (Ganopristodus, Traq.). Body laterally compressed, with small and very thin scales, which are faintly striated. Paired fins acutely lobate. Dorsal fin arising shortly behind the head. U. lobatus, Traq., from Lower Carboniferous (Calciferous Sandstones), Burdiehouse, near Edinburgh. Conchopoma, Kner. Lower Permian ; Rhenish Prussia. Family 2. Ctenodontidae. Traquair. A pair of dental plates on the palatine bones, and an opposing pair on the splenials; these plates usually retaining traces of their component denticles. Jugular plates usually present. Tail diphycercal or heterocercal. Dipterus, Sedgw. and Murch. (Catopterus, Polyphractus, Ag.), (Figs. 114, 115). Small fishes. Bony plates of head covered with punctate ganoine, but cranium apparently quite cartilaginous. Base of cranium covered with a Fig. 114. Dipterus Valenciennes!, Sedgw. and Murch. Restoration, i/ s nat. size. Lower Old Red Sandstone ; Banniskirk, Orkney (after Pander). broad, rhombic parasphenoid (PSph), which is flanked on either side by a pterygo- palatine (P) extending forwards into a triangular pointed plate, which serves as base for a large triangular tooth (d) bearing tuberculated radiating ridges. The two palatine bones meet in the middle in a straight line. The mandible is com- pletely ossified, with a single, large dental plate on PSvh Fig. 115. Wpterv.8 valenciennesi, Sedgw. and M. Lower Old Red Sandstone; Banniskirk. A, Roof of skull. B, Ini- pertect palate (PSph, Parasphenoid ; 1>, Pterygo -palatine, accidentally divided into two pieces behind by a broken line ; ( /, Palatine tooth). C, Tniperfect mandible with tooth (J), after Pander). the splenial of each side, and its tuberculated ridges radiating fan-like from SUB-CLASS IV DIPNOI 63 within outwards. Two pairs of jugular plates. Paired fins acutely lobate, the pelvic pair remote and opposed to the anterior of the two dorsal fins ; anal fin opposite the posterior dorsal ; tail heterocercal. Trunk and fins covered with thick, deeply overlapping scales, which are nearly rhombic in their exposed portion and invested with punctate ganoine. Complete, but mostly flattened and distorted examples of Dipterus are not uncommon in the Lower Old Red Sandstone of Northern Scotland. Dental plates very abundant in Middle and Upper Devonian of central and eastern United States. Scanmenacia, Traq. Upper Devonian ; Canada. Phaneropleuron, Huxley (Fig. 117). Upper dental plates triangular, with straight and crenulated radiating ridges. Long; dorsal fin continuous with the caudal, but small anal fin separate. Scales very thin and cycloid, marked P. ander- known by well - preserved specimens from Upper Old Red Sand- stone, Fifeshire. Palaedaphus, van Beneden (Heliodus, Xewb.), (Fig. 118). Only known by mandible and detached dental plates. In ^SSffSS^!^&. P. insiqnis, van Ben. and de Koninck, each Newsham, Northumberland (after Hancock and u , , , . r\ -i fr Atthey). Oral surface of teeth really concave. lower dental plate, measuring lrl7 m. in length, bears four smooth, obtuse radiating ridges. Upper Devonian ; Belgium and Pennsylvania. ( 'dnchodus, M'Coy ; Synthetodus, Eastman. Devonian. Ctenodus, Ag. (Fig. 116). Hinder border of cranial roof with one median occipital plate, with a pair of plates immediately adjoining in front. Dental with delicate radiating striae soni, Huxl., Fig. 116. Pterygo-palatim Coal Measures Fig. 117. Phaneroplewon andersoni, Huxley. Upper old Red Sandstone ; Dura Den, Fifeshire. V;; nat. size (after Page). plates with numerous tuberculated or crenulated radiating ridges. Dorsal 64 PISCES CLASS I and anal fins continuous with the caudal, which is diphycercal ; scales very large and thin, without a ganoine layer, almost quadrate in shape, but with rounded angles ; marked more or less distinctly with reticulations, as in Ceratodus. Dental plates common in the Carboniferous of Europe and North America ; fine portions of skeleton in the English Coal Measures. Sagenodus, Owen (Megapleuron, Gaudry; Ptyonodus, Cope). As Ctenodus, but dental plates with fewer ridges, and median occipital plate with another unpaired plate im- mediately in front of it. Scales and dental plates common in the Carboni- ferous and Lower Permian of Europe FlG ' 11S ' and North America : fine skeletons in Palaedaphus insiqnis, van Beneden and de Koninck. . <• -r> i • i Imperfect inaudible, i/ 4 nat. size. Devonian ; Liege, the Lower Permian 01 Jbohemia and , Tooth; d, Dentary; op, Splenial; y, Lateral fossa. Xj\.„r,„ p (after Traquair). x 1 tillLt! - Order 2. SIRENOIDEI. Cranial roof bones large and few. Rays of median fins very fine, much more numerous than their supports, which are directly apposed to the vertebral arches. Family 1. Lepidosirenidae. A pair of dental plates on the palatine bones, and an opposing pair on the splenials ; also a pair of small cutting teeth on the vomer. Jugular plates absent. Median fin continuous, and tail diphycercal. Body covered with thin, elastic, cycloid scales without a bony basis. Triassic to Recent. Of the three genera referable to this family, Lepidosiren lives in the tropical swamps of South America, Protopterus in those of Africa, and Ceratodus in the rivers of Queensland. Ceratodus, Ag. (Fig. 119), is covered with large, thin cycloid scales; the dorsal and anal fins are continuous with the diphycercal caudal. The pectoral and pelvic fins are fringed with membrane stiffened by fine rays. The upper vertebral arches, spinous processes, ribs, and fin supports are encased in thin bony sheaths. The flattened roof of the skull consists of two large median plates, one behind the other, and two pairs of lateral plates. On the lower side of the chondrocranium there occurs the long parasphenoid {PSph), with its rhombic anterior expansion flanked on either side by the pterygo-palatines (Pt). The latter bones meet in a median suture in front, and each bears a large triangular dental plate (d), with radiating ridges. . The vomerine carti- lage (Vo) bears a pair of sharp, chisel-shaped teeth (d r ). On the splenial of each ramus of the mandible there is also a dental plate with deep, radiating ridges. The opercula, sub-opercula, hyoid bones, and branchial arches are ossified ; the quadrate remains cartilaginous. In the living Ceratodus (Epiceratodus, Teller), the upper and lower dental SUB-CLASS V GAXOIDEI 65 plates bear six ridges radiating outwards. The corresponding plates occurring in the Trias, namely, in the bone beds of the Muschelkalk, Lettenkohle, and Rhaetic, are distinguished by their larger size and a different number of ridges. As a rule, the upper dental plates exhibit five, the lower ones only four radiating ridges. The oldest known species (C. areriaceus, Quenst.) was Fig. 119. Ceraiodus forsUri, Krefft. Lateral aspect offish (A), base of skull (B), and mandible (C). Recent ; Queens- land. Br, Branchial cavity ; c, Foremost rib ; d, Teeth ; na, Nasal openings ; PSph, Parasphenoid ; Ft, Pterygo- palatine ; Qu, Quadrate ; Vo, Vomer (after Gunther). D, Ceratodus kaupi, Ag. Mandibular tooth on bony base, 1 /;; nat. size. Lettenkohle; Hoheneck, near Ludwigsburg. obtained from the Bunter Sandstone of Wurteinberg ; the latest, which are the smallest, are discovered in Europe in the Bathonian of Stonesfield and Northampton, England, in North America in the Upper Jurassic of Colorado. Other examples occur in the Kota-Maleri beds of India, in the Karoo Formation of South Africa, and in later deposits in Patagonia. A well- preserved skull of C. sturi has been described by Teller from the Upper Keuper of Polzberg, near Lunz, in Lower Austria. Sub-Class 5. GANOIDEL Agassiz. 1 Enamel-scaled Fishes. Trunk and tail usually covered with ganoid scales, rarely naked or with bony plates. Skull covered with dermal bones, or completely ossified; pterygo-quadrate arcade morally articulated with the cranium (hyostylic) ; gill clefts feebly separated, opening into a cavity covered with a bony operculum. Vertebral column cartilaginous, or with various degrees of ossification. Fin rays articulated, and fulcra usually 1 Cope, E. B., Trans. Amer. Phil. Soc. vol. XIV. 1871, p. 445; and Amer. Nat. vols. XIX., XX., XXL, XXIII. (1885-89).— Huxley, T. H., Preliminary Essay upon the Systematic Arrange- ment of the Fishes of the Devonian Epoch (Mem. Geol. Snrv. dec. X.), 1861. — Kner, R., Betrach tungen uber die Ganoiden als natiirliche Ordnung (Sitzungsb. k. Akad. Wiss. Wien, matn.-naturw. CI. vol. LIV.), 1866. — Lutken, Chr., Ueber die Begrenzung und Eintheilnng der Ganoiden (Palaeontogr. vol. XXII.), 1868. — Muller, Joh., Ueber den Bau und die Grenzen der Ganoiden (Abhandl. k. Akad. Wiss. Berlin, 1834), 1836. — Traquair, R. 1_L. The Ganoid Fishes of the British Carboniferous Formations. I. Palaeoniscidae (Palaeont. Soc), 1877, No. 2, 1901. — Vogt, ''.. Quelques Observations qui servent a la Classiticatiou des Ganoides (Ann. Sci. Nat.. Zool. ser. 3, vol. IV. . VOL. II F 66 PISCES class r present. Paired fins well developed , tail diphycercal, heterocercal, or hemi-heterocercal. In the living forms — optic nerves not completely decussating but forming a chiasma, bulbus arteriosus of the heart with numerous valves, intestine with a spiral valve, and air-bladder connected by a tube with the gullet. When founding the " order " of Ganoids, Agassiz paid attention exclusively to the dermal skeleton, and included under this denomination all fishes with scales which consisted of a bony lower layer and a superficial covering of enamel. Johannes Midler first attempted to define the Ganoids from anatomical characters. After the removal of the Plectognathi, Lophobranchii, and Siluroids recognised as true bony fishes, and after the assignment of Lepidosiren to the Dipnoi, there still remained as true Ganoids a large number of recent and fossil fishes, which, according to Johannes Miiller, formed a distinct sub-class between the Selachii and the bony fishes. While the condition of the muscular bulbus arteriosus, the incomplete decussation of the optic nerves, and the spiral valve in the intestine agree with the former, the arrangement of the head bones, the structure of the fins, and usually also the ossification of the skeleton, are suggestive of the bony fishes. After C. Yogt had recognised in the anatomical structure of Amia a true Ganoid, with thin elastic cycloid scales and a completely ossified skeleton, the line of demarcation between the Ganoidei and Teleostei seemed to have been absolutely destroyed. Kner, Thiolliere, Owen, and more recently Cope and Smith Woodward have ventured still further, suppressing the Ganoidei as a separate group, and uniting its members with the Teleostei under the general denomination of Teleostomi. The most conspicuous, even if not the distinctive feature of the Ganoids, consists in their dermal covering. No other sub-class of fishes possesses scales which consist of a thick bony inner layer and an outer enamel layer. In no other group is there a union of scales by peg-and-socket articulations, such as is characteristic of the rhombic-scaled Ganoids. There are, however, ganoid scales of rounded form, which overlap each other exactly like cycloid and ctenoid scales, and which are sometimes not perceptibly thicker than the latter ; but these rounded scales (Caturus, Megalurus, Macrorhipis, Amia) exhibit beneath the enamel covering an inner layer with bone cells, though sometimes its thickness is excessively reduced. The Spatularias are characterised by the complete absence of scales, except on the upper lobe of the tail ; in the Sturgeons the body is partly covered with large bony plates. The structure of the internal skeleton of the Ganoids is of special interest, notably that of the vertebral column. In some Chondrostei (Acipeuser) the vertebral axis, with its arches and spines, remains completely cartilaginous ; but in Spatularia, the older Crossopterygii, almost all Heterocerci and Pycnodonts, and part of the Lepidostei, there is a partial or complete ossification of the arches, spinous processes, and supports of the median fins, this beginning at the surface and extending inwards, so that a cartilaginous core is usually surrounded by a hollow bony cylinder. These are termed " naked vertebrae " (Nacktwirbel), (Fig. 120), in contradistinction to the so-called " hemi-vertebrae '" (Halbwirbel), and "ring vertebrae" (Hohlwirbel). In the first (Fig. 121) there develops below the notochord a horseshoe-shaped bony plate (hypocentrum. intercentrum), to which the haemal arches in the caudal region are fixed ; the upwardly directed side-pieces of these hypocentra are mostly attenuated and pointed. The vertebral centrum proper is represented by a pair of lateral SUB-CLASS V GANOIDEJ 67 bony plates (pleurocentra), which are usually pointed below and frequently fused together dorsally, thus forming a second horseshoe-shaped half-ring. According to their size the hypocentra and pleurocentra more or less completely surround the soft, unsegmented notochord. Sometimes when the upper and lower lateral pieces do not tapei- but continue of uniform width, and meet together Fig. 120. Two caudal vertebrae of Pyciwdus platessus, Ag. (after Heckel;. .1 li y< Fig. 121. Vertebrae of Euthynotus (A), and Caturus Jurcatus, Ag. (B). hyc, Hypocentrum ; n, Neural arch; p, Parapophysis ; pic, centrum ; sp, Cleft neural spine. '•, Rib; Pleurn- dorsally and ventrally, they form two half -rings, which completely enclose the notochord (Fig. 121). In many genera (E urycormus) the anterior abdominal region consists of half vertebrae, while the caudal region consists of ring vertebrae, which are composed of two halves (Fig. 122). By the complete fusion of the two half rings, there arise simple, sheath-like ring vertebrae (Fig. 122). In the Amiidae the vertebral centra of the abdominal region A Fig. l •_"_'. A , Caudal vertebrae of Eurycorm us speciosus, Wagn. ]:, Verte- braeof Amia calva, Linn. From anterior part of caudal region. h, Haemal arch; hyc, Hypocentrum; n, Neural arch; pic, Pleurocentrum. Fig. 123. Aspidorhynch us, sp. Caudal vertebrae, each bearing a neural and haemal arch. are completely ossified and amphicoelous, while some of those of the caudal region are still divided into two halves, which correspond with the hypo- and pleuro-centra of the Lepidostei (Fig. 122, B). The complete ossification of the vertebral column, as in the beny fishes, is observed only among the latest representatives of the Ganoids, namely, the Polypteridae and the Lepidosteidae. Among the latter, moreover, the verte- bral centra are only concave behind, convex in front (opisthocoelous). The hinder end of the vertebral column is always produced into the caudal tin. The true diphycercal condition (see p. 8) constantly persists in some ( Vossopterygians (Coelacanthidae) and Chondrosteans (Belonorhynchidae). In most Crossopterygians the caudal fin is hetero-diphycercal, that is, the vertebral column extends straight, but the rays of the upper lobe of the fin are more delicate and shorter than those of the lower lobe. True heteroceraj and 68 PISCES class i hemi-heterocercy (internal heterocercy, external homocercy, see p. 10) are very common. In many Ganoids the unpaired fins, and sometimes also the paired fins, are fringed on the anterior border with the so-called fulcra — scale-like spines or plates covered with enamel, which are serially arranged and partly overlap one another. All the fin rays consist of two (right and left) halves, and are transversely jointed, usually also branched distally. Like the vertebral column, the skull also exhibits very variable degrees of ossification. In the cartilaginous Ganoids this is almost exclusively confined to a number of investing plates on the cranial roof and the basicranial axis. The pterygoid and palatine bones are still fused together ; the mandible and parts of the hyoid apparatus are ossified ; the opercular apparatus is feebly developed. In the Crossopterygii, Heterocerci, and Lepidostei the ossification closely resembles that of the Teleostei, while the number and arrangement of the several bones agree essentially with the corresponding features in some of the least specialised members of the latter sub-class. In the structure of the pectoral arch, and especially of the anterior limbs, the various orders of Ganoids exhibit considerable differences, and represent intermediate links between the Dipnoi, Selachii, and Teleostei. In the Crossopterygii, Chondrostei, and Heterocerci the clavicle still consists of three separate membrane bones ; while in the Lepidostei and Amioidei the lower segment (infraclavicle) is completely fused with the clavicle. The small structures behind and within the clavicle, corresponding with the scapula, coracoid, and precoracoid remain cartilaginous in the Chondrostei, probably also in the fossil Crossopterygii ; in the remaining Ganoids, on the other hand, they are ossified exactly as in the Teleostei. Moreover, with reference to the position and number of the basal supports in the pectoral fins, most Ganoids agree with the bony fishes ; the earlier Crossopterygii alone possessed a segmented cartilaginous axis, with biserial radialia, as in the Dipnoi. Besides the anatomical characters in the dermal covering and the internal skeleton there are still others indicating that the Ganoids are a natural group of fishes. For example, the somewhat elongated muscular base of the principal artery (bulbus arteriosus) is provided internally, as in the Selachii, with several rows of valves, which prevent the return of the blood from the artery to the auricle of the heart. The gills, on the other hand, as in the Teleostei, always lie free under an operculum, which usually consists of several bony plates. Again, by the possession of a spiral valve in the intestine, as well as in the structure of the urinogenital system, the Ganoids approach the Selachii more closely than the Teleostei ; on the other hand, they all possess an air-bladder opening into the gullet, and also produce numerous small eggs. By the complete decussation of their optic nerves, the Teleostei are distinguished from the Ganoidei, in which the branching optic nerves form a so-called chiasma. The Ganoids exhibit their greatest development in Palaeozoic, Triassic, and Jurassic formations ; and from the base of the Cretaceous system upwards they become more and more replaced by the bony fishes. The few still existing Ganoids live either exclusively, or at least partly, in fresh water, while the large majority of the fossil forms occur in purely marine deposits. As a rule, only the Tertiary Ganoids occur in freshwater formations. The Ganoidei maybe divided into five orders : — (1) Crossopterygii; (2) Chondrostei ; (3) Heterocerci ; (4) Lepidostei ; (5) Amioidei. SUB-CLASS V GAXOIDEI 69 Order 1. CROSSOPTBRYGII. Huxley. Fringe-finned Ganoids. Notochord persistent or vertebrae ossified. Tail diphy cereal or hetero-diphycercal. Infra clavicle present. Paired fins with a scab/ axis fringed on both titles by dermal rays. BranchMegal apparatus between the rami of the mandible consisting of a pair of large jugular plates, these in many Palaeozoic genera flanked by a series of small lateral jugulars and an anterior median plate. Ganoid scales rhombic or cycloidal, completely covering the trunk and. tail. Family 1. Holoptychiidae. Traquair. Body covered with imbricating, cycloidal ganoid scales. No ossified vertebrae. mmmim ffiW^i l|liiiiii^ :: ' Wmmmz *% Fig. 124. Holoptychius nobilissimus, Ag. Upper Old Red Sandstone ; Scotland (restoration after Huxley Pectoral fins acutely lobafe. Two dorsal fins and one anal fin, each borne by a single i distally expanded support (axonost), followed by one or two rows of short basal pieces (baseosts), which support the very numerous, Fig. 125. Scale of Holoptychius (Glyptolepis). Outer (A), and inner (B) aspect. Old Red Sand- stout- : Wik, Russia (after Pander). Fig. L26. Dendrodus biporcatus, Ag. Tooth in side view (A), and from below (B), nat. size, and transverse section of the same (C), highly magnified (after Pander). fine, dermal fin rays. Lateral jugular plates, clavicle, and infraclavicle present. 70 PISCES CLASS I Head and branchial region covered with enamelled dermal bones. Teeth numerous, acutely conical, arranged on the border of the jaws : enlarged laniary teeth in a second inner series on several separate splenial bones. The teeth distinguished by a very complicated, meandering, folded structure (dendrodont). Devonian. The only satisfactorily known genus referable to this family is Hoi opt //chins, Ag. (Glyptolepis, Platygnathus, Ag.), (Figs. 124, 125), from the Old Red Sand- stone of Scotland, England, and Ireland, and from the Devonian of N.-W. Russia, Bohemia, Belgium, the Eifel, the United States, Canada, and Green- land. Several species attain a large size. Detached teeth have been described as Dendrodus, Owen (Fig. 126); Lamnodus, Ag. ; and Apedodus, Leidy. Family 2. Rhizodontidae. Traquair. Closely resembling preceding family, but both paired fins with a short, obtuse lobe. Teeth few and cortical, with a well-defined pulp carity, the wall of which is radio tely m T- FjG. 127. Rhizodus hihberti, Ag. Tooth, !/o nat. size. Lower Carboniferous ; Edinburgh. folded in the lower part of the crown. Usually several tooth -bearing splenial bones on the inner side of the mandible. Devonian, Carboniferous, and Lower Permian. Rhizodus, Owen. (Megalichthys, Ag. p.p.), (Fig. 127). Very large, incom- pletely known fishes with rough, rugose cycloidal scales. Infraclavicle with a long upwardly directed process. Teeth smooth, compressed to a sharp edge in front and behind. R. hihberti, Ag., and B. ornatus, Traq., from Lower Carboniferous, Scotland and North- umberland. Allied species in Coal Measures of North America. Fig. 12S. Rhizodopsis sauroides, Williamson s]>. Outline re- storations of head and opercular apparatus from the upper (A), lower (B), and lateral (C) aspects, about 1/2 nat. size. Upper Carboniferous ; Staffordshire, ag, Angular; d, Dentary;/, Frontal; id, Infradentary : j, Principal gular (jugular) ; Ij, Lateral gular (jugular): wj, Median gular (jugular); mm,, Mandible; nix, Maxilla; op, Operculum; or, Orbit; pf, Postfrontal ; pmx, Premaxilla ; pop, Preoperculum ; pa, Parietal; so, Suborbital ; sop, Suboperculum : sq, Squamosal ; st, Supratemporal ; x, <', Cheek-plates (after Tra- quair). SUB-CLASS V GANOIDEI 71 Strepsodus, Young (Dendroptychius, Young ; Archichthys, Banc, and Attb.). Large and medium- sized fishes with slender and somewhat curved teeth, which are not compressed to sharp edges. S. sauroides, Binney sp., from Coal Measures of England, Scotland, and Ireland. Other species from Lower Carboniferous of Scotland, Ireland, and Nova Scotia. Bhizodopsis, Young (Dittodus, Ganolodus, Characodus, Gastrodus, Owen). (Fig. 128). Scales oval, with an extremely thin layer of punctate ganoine. Teeth round in section, smooth. Vertebral axis with ring vertebrae. The small type species represented by fine examples in the English Coal Measure 3 Fragments in the Coal Measures of Silesia, Nova Scotia, and Illinois. Gyroptychius, M'Coy; Tristichopterus, Egerton ; Eusthenopteron, Whiteaves ; Polyplocodus, Pander ; Sauripterus, Hall. Devonian and Old Red Sandstone : Europe and North America. Family 3. Osteolepidae. Smith Woodward. Body slender, covered with rhombic ganoid sea Irs. Pang vertebrae at least in the caudal region. Paired fins with a short, obtuse lobe. Teeth conical, only externally folded at the base, as in Bhizodcmtidae. Devonian and Carboniferous. Osteolepis, Ag. (Tripterus, Triplopterus, M'Coy), (Fig. 129). Cranial roof bones in advance of the parietals fused into a continuous shield, pierced by a Fig. l'2y. Ostt olepis macrolepidotus, Ag. Lower Old Red Sandstone ; Scotland (restoration after Pander). median frontal (pineal) foramen. An anterior median jugular plate present. Teeth round in section. First dorsal fin in front of the pelvic pair. Scales smooth and punctate. 0. macrolepidotus, Ag., and 0. microlepidotus, Pander. Lower Old Red Sandstone ; Scotland. Thursius, Traq. As Odeolepis, but first dorsal opposite pelvic fins. Lower Old Red Sandstone ; Scotland. Diplopterus, Ag. Lower Old Red Sandstone ; Scotland. Megalichthys, Ag. (Centrodus, M'Coy ; Bhomboptychius, Young ; Edosteorhachis, Cope). Cranial roof bones in advance of the parietals rarely fused into a continuous shield, without a median frontal foramen. Teeth round in section. First dorsal tin nearly opposite : -^lS^ the pelvic pair. Scales smooth and punctate. Carboni- ferous of Great Britain and North America. Lower Permian of Texas. M. hibberti, Ag., the best known British species from the Coal Measures. i i ... 130. Glyptopomus, Ag. (Glyptolaemus, Huxley), (Fig. 130). Giyp < kinnairdi, Bones of cranial roof not fused together: a median upper Old Red ' Sandstone • frontal (pineal) foramen. External bones' and scales £S ey £ en ' V ^ >hU " ^ ornamented with irregular reticulating rugae or fused series of tubercles. Upper Old Red Sandstone : Scotland, possibly also Belgium and Pennsylvania. 72 PISCES CLASS I Family 4. Coelacanthidae. Huxley. 1 Body covered with thin, cycloidal ganoid scales. No ossified vertebrae. Arches, spinous processes, and supports of caudal fin superficially ossified. Air bladder ossified. Paired fins with a short, obtuse lobe. Each of the two dorsal fins and the anal fin supported by a simple, usually proximally forked plate, which in the anterior dorsal is in direct contact with the dermal rays. Caudal fin distinctly diphy cereal, borne above and below by numerous simple supports, and terminating in a small pro- jecting tufted fin. Only one opercular bone on each side and a pair of jugular plates ; but several splenial bones present. Upper Devonian to Upper Cretaceous. Coelacanthus, Ag. (Hoplopygus, Ag. ; Conchiopsis, Cope ; Bhabdoderma, Reis). Teeth absent on the margin of the jaws, but a few hollow, conical teeth within. Supplementary caudal fin prominent. External bones and scales ornamented with series of tubercles or fine ridges of ganoine ; fin rays not denticulated. Carboniferous and Permian of England, Scotland, 'Germany (Kupferschiefer), and North America. Fragments probably also in Upper Devonian of Harz Mountains. Graphiurus, Kner ; Heptanema, Bellotti. Trias of Raibl and Perledo. Diplurus, Newb. Trias ; New Jersey and Connecticut. Undina, Miinster (Holophagus, Egerton), (Fig. 131). Supplementary caudal fin prominent. All the fin rays robust, broad, and closely articulated Fig. 131. Undina penicUlata, Miinst. Upper Jurassic (Lithographic Stone) ; Landt, near Eichstadt. 1/3 (after Huxley). ./', Jugular plates ; b, Scales from upper region of trunk of Undina acutidens, Reis. W^m/i'-w distally ; the anterior rays of the first dorsal and caudal fins denticulated or tuberculated. External bones and scales rugose and tuberculated. Lower Lias to Lower Kimmeridgian. Libys, Miinst.; Coccoderma, Querist. Lithographic Stone (Lower Kim- meridgian) ; Bavaria and Wiirtemberg. C. substriolatum, Huxl. sp., from Kimmeridge Clay, England. 1 Huxley, T. If., Illustrations of the Structure of the Crossopterygian Ganoids (Mem. Geol. Surv. dec. XII.), 1866.— Iteis, 0., Die Coelacanthinen (Palaeontogr. vol. XXXV.), 1888; also Geogn. Jahresh., Miinchen, 1892. SUB-CLASS V ( JANOIDEI 73 Macropoma, Ag. Maxilla, vomer, and palatine with conical teeth. Sup- plementary caudal fin unknown. Fin rays robust and straight, not expanded distally, with distant articulations ; a double series of small, upwardly pointing denticles on nearly all the rays of the first dorsal and caudal fins. Turonian and Senonian of Europe. M. mantelli, Ag., especially well preserved in the English Chalk. Family 5. Polypteridae. Huxley. Body covered with thick, rhombic ganoid scales. Vertebrae and the complete internal skeleton ossified. Tail diphycercal. Pectoral fins with short, obtuse lobe, the numerous, short, fan-like basalia attached to two diverging bones (propterygium and metapferygium) and a median mesopterygium. Dorsal fin single, remarkably extended, the spine-like rays borne by a corresponding number of supports. Only a single pair of jugular plates. Teeth sharply ^^s^^M^^^^^^MMt conical, with simple pulp cavity. Recent. Fig. 132. Polyptcrus bicMr, Geottr. Recent ; Upper Nile. To this family be- long the two genera, Polypterus (Fig. 132) and Calamoichthys, living in the rivers of tropical Africa. Order 2. CHONDROSTEI. Cartilaginous Ganoids. Notochord persistent, and endoskeleton chiefly cartilaginous ; head covered with bony dermal plates. Teeth small or wanting. Opercular apparatus imperfectly developed, the branchiostegal rays usually absent. Infraclavicle present. Paired fins without a scaly axis, but each pelvic fin with a row of cartilaginous basal supports. A single dorsal and anal fin, with dermal rays more numerous than their supports. Caudal fin heterocercal (rarely diphycercal), and the upper lobe usually covered with rhombic scales. Trunk almost or completely naked, or with rows of bony plates. Family 1. Chondrosteidae. Smith Woodward. 1 Parietal and frontal bones paired ; a large squamosal bordering the parietal s on each side. Jaws toothless, and premaxilla absent. Operculum small, suboperculum large ; a few branchiostegal rays present. Trunk naked, only the upper fulcrated lobe of the tail with elongated, oat-shaped ganoid scales. Lias. Chondrosteus, Egerton. Mouth very small and inferior ; jaws toothless ; maxilla arched, much expanded behind and tapering in front. About ten branchiostegal rays, but no gular plate. Dorsal fin short-based, opposed to the pelvic pair. Trunk naked. C. acipenseroides, Eg., about a metre in length, known by nearly complete skeletons from the Lower Lias of England. Gyrosteus, Sm. Woodward (ex Ag. MS.). Usually much larger than Chondrosteus, and the toothless maxilla expanded in its front portion for a palatine articulation. G. mirabilis, Sm. Woodw. (ex Agassiz, MS.), represented by fragments in the Upper Lias of Whitby. 1 Woodward, A. S., On the Palaeontology of Sturgeons (Proc. Geol. Assoc, vol. XL), 1889 ; also Proc. Yorks. Geol. and Polyt. Soc. vol. XIII. 1898, p. 461. '4 PISCES CLASS T Family 2. Acipenseridae. Sturgeons. Elongated fishes with a produced snout, and small toothless mouth without pre- maxilla. Parietal and frontal bones large, nonsymmetrical, and granulated. Oper- culum incompletely developed, not quite covering the branchial opening ; branchiostegal rays absent. Dorsal and anal fins borne by two roivs of sujjports (axonosts and baseosts) ; ca udal fin strongly heterocercal, the large upper lobe ridged with fulcral scales. Trunk with five longitudinal series of keeled bony plates. Tertiary and Recent. The sturgeons of the two living genera, Acipenser and Scaphirhynchus, inhabit the seas of the northern hemisphere, and enter the rivers of Europe, Asia, and North America. Fossil remains are rare. An Eocene species (Acipenser toliapicus, Ag.) is represented by scutes in the London Clay of Sheppey. Scutes and pectoral fin rays are also known from Upper Eocene and later deposits in Europe, and from the Miocene of Virginia, U.S.A. Family 3. Polyodontidae. Paddle-fishes. Snout very long and spatulate. Parietal and frontal bones paired. Mouth large, with minute teeth in both jaws; no premaxilla. Branchiostegal rays absent. Scales rudimentary or absent, except on the sides of the upper caudal lobe, which is ridged with large fulcral scales. Cretaceous (?) or Eocene to Recent. Crossopholis, Cope. Rostrum covered with small stellate bones. Scales of trunk small, thin, and separated ; each being a grooved disc with posterior denticulations like a fringe. C. magnicaudatus, Cope ; Eocene (Green River Shales), Wyoming. Pholidwrus, Sm. Woodw. Known by caudal ridge scales only, from the Upper Chalk, Kent. Polyodon (Spatularia) living in the Mississippi, Psephurus in Chinese rivers. Family 4. Belonorhynchidae. Smith Woodward. 1 Slender fishes with a much elongated, pointed snout. Mouth very large, and jaws with numerous conical teeth of different sizes. Opercular apparatus reduced, without branchiostegal rays. Fin fulcra minute or absent ; dorsal and anal fins small and remote ; caudal fin diphycercal. Trunk with four longitudinal rows of small, keeled, scale-like plates. Trias and Lias. Belonorhynchus, Bronn. (Ichthyorhynchus, Bellotti ; Saurorhynchus, Reis.), Fig. 133. FMonorhynehus striolatus, Bronn. Keuper; Raibl, Carinthia. Nat. size. (Fig. 133). Head and trunk excessively elongated. Jaws approximately equal in length, and mandible remarkably deep behind. Head bones exter- 1 Woodward, A. S., The Fossil Fishes of the Hawkesbury Series (Mem. Geol. Surv. N. S. Wales, Palaeont. No. 4), 1890.— Reis, 0., Geogn. Jahresh., IV. Miinchen, 1891. actum- sub-class v GAN0IDE1 75 nally ornamented with striae, rugae, or . reticulations. The remote dorsal and anal fins opposed to each other ; the diphycercal caudal fin truncated at its hinder margin. Of the four series of imbricating keeled dermal scutes one extends along the back, another along the ventral border, and the other two smaller series along the Hanks. The ventral scutes form a ring round the region of the anus. Belonorhynchus occurs in the Trias of the Alps (Raibl, Perledo, Seefeld) and Australia (Hawkesbury Forma- saurichthys tion), and is represented by skulls and other fragments in »■"'"*■ . A -- To f* Mr ■> o iiat. S1Z6. Iuia*'Tic ' the Lias of England and Germany (Belonostomus acutus, Ag.). Kemnath.Wurt'em- The teeth, jaws, and skulls from the Muschelkalk, Keuper, and Rhaetic, described under the name of Saurichthys, Ag. (Fig. 134), probably belong to Belonorhynchus. Order 3. HETEROCERCI. Zittel. 1 Notochord persistent, but arches, spinous processes, and fin supports more or less ossified; head covered ivith bony dermal plates. Opercular apparatus well developed, and branchiostegal rays numerous. Infraclavicle present. Unpaired, and usually also paired fins fringed with fulcra. Paired fins without scaly axis, but each pelvic fin with a row of imperfectly ossified basal supports. A single dorsal and anal fin, with articulated rays which are more numerous than their supports. Caudal fin heterocercal. Scales rhombic or rhomboidal, rarely cycloidal. In their skeletal structure and the characters of their paired fins, the Heterocerci agree so closely with the Chondrostei, that they are united with the latter by Traquair under the ordinal name of Acipenseroidei. In their outward aspect they bear a superficial resemblance to the Lepidostei. The Chondrostei, Heterocerci, and Lepidostei, probably form three different specialised branches from one and the same primitive group. Family 1. Palaeoniscidae. Vogt emend. Traquair. Trunk elongate-fusiform. Head bones more or less enamelled. Teeth slender, conical or styliform. Scales ganoid, rhombic in shape, rarely cycloid on the trunk. Devonian to Upper Jurassic. Gheirolepis, Ag. Jaws with an outer row of minute teeth and an inner row of stouter teeth. Dorsal fin remote, arising behind the origin of the anal fin. Scales very small, rhombic, or almost square. C. cummingiae, Ag. ; Lower Old Red Sandstone, Scotland. C. canadensis, Whiteaves. Upper Devonian : Scau- menac Bay, Canada. Canobius, Gonatodus, Traquair. Lower Carboniferous ; Scotland. G. moly- neuxi, Traq. ; English Coal Measures. Amblypterus, Ag. Mouth and teeth small. Fins with delicate fulcra. Scales smooth. Several species from Lower Permian (Rothliegendes) of Rhenish Prussia, Bohemia, and France. A. latus, Ag. ; A. duvernoyi, Ag. sp. Eurylepis, Xewb. (Fig. 135). Small fishes with small fins, the fin rays not 1 Traquair, 11. II.. The Ganoid Fishes of the British Carboniferous Formations Palaeont. Soc.) No. 1, 1877, No. 2. 1901. — On Amblypterus, Palaeoniscus, Gyrolepis, ami Pygopterus (Quart. Journ. Geol. Soc. vol. XXXIII. ), 1S77.— On Eskdale Fishes (Trans. Roy. Soc. Edinb. vol. XXX.), 1881. 76 PISCES CLASS I divided distaily, and the caudal obliquely truncated. Teeth small. Scales rugose, denticulated on the hinder border ; two or more rows of scales on the flank remarkably deepened. Coal Measures ; Ohio, and rarely England. Nematoptych ius, Bhadinichthy?, Traquair ; Cycloptychius, Young. Carboniferous. Pygopterus, Ag. Kupfer- schiefer. Palaeoniscus, Blv. emend. Tra- quair (Fig. 136). Slender fishes, small or of moderate size. Teeth sharply pointed, of different sizes. Fins small, the ravs articulated and divided distally. Dorsal in front of the anal fin. Scales rhombic, marked with irregular oblique furrows. Km Fig. 135. ylepis tuberculatus, Newb. Coal Measures ; Linton, Ohio. Fig.136. . ■ Palaeoniscus macropomus, Ag. Restora- tion of head (^4), pectoral arch (B), and caudal fin (C). Natural size. Kupfer- schiefer ; Thuringia. «/, Anterior frontal ; ag, Angular ; br, Branchiostegal rays ; el, clavicle ; d, Dentary ; e, Ethmoid ; /, Frontal ; id, Infraclavicle ; top, Suboper- culum ; mx, Maxilla; n, Narial opening; op, Operculum ; p, Parietal ; pel, Post- clavicle ; pop, Preoperculum ; pt, Post- temporal ; jmix, Premaxilla ; q, Squa- mosal ; sd, Supraclavicle ; so, Circum- orbital ring and suborbitals ; st, Supra- temporal. Dotted lines indicate course of sensory canals (after Traqnair). P. Jreieslebeni, Blv. (Fig. 136), and other species very common in the Kupfer- SUB-CLASS V GANOIDEI » i. schiefer of Thuringia and Riechelsdorf, Hesse ; also found in the Upper Permian of England, France, and Russia. Elonichthys, Giebel (Bhabdolepis, Troschel ; Cosmoptychius, Traquair), (Figs. 137, 138). Teeth of different sizes. Fins large, with fulcra, and the rays distally divided. Dorsal in front of the anal fin. Scales rhombic, obliquely sculptured. E. germari, Gieb., from Coal Measures of Saxony. Other species A B Fig. 137. Elon ichthys (Cosmoptych ius) striatus, Ag. sp. Scale from outer (A), and inner (B) aspects, three times nat. size. Lower Carboniferous ; Edinburgh (alter Traquair). Fig. 13S. Elonichthys (Rhabdolepis) macropterus, Bronn sp. Lower Permian (Roth- liegendeii), Lebach. near Saarbriieken Rhenish Prussia (restoration after Agassiz;. Fig. 139. Gyrolepis ornatus, Gieb. Scales enlarged. M uschel- kalk ; Esperstadt (after Dames). An allied fish from the Carboniferous of England, Scotland, and North America ; also from the Lower Permian of Rhenish Prussia and Bohemia. Acrolepis, Ag. Closely resembling Elonichthys, but scales more deeply over- lapping. A. sedgwicki, Ag., from Upper Permian (Marl Slate of Durham and Kupferschiefer of Germany). Other species in Carboni- ferous of England, Scotland, and Belgium. Gyrolepis, Ag. (Fig. 139). Anterior rays of pectoral fins not articulated. Operculum deep and narrow. Scales marked with irregular oblique and curved rugae. Common in the Muschelkalk and Rhaetic Bone-bed, but usually only isolated scales. Jlyriolepis, Egerton. Scales very small. M. clarkei, Eg., from Trias (Hawkesbury Formation), New South Wales in the Coal Measures of Kilkenny, Ireland. Oxygnathus, Egerton (Thrissonotus, Cosmolepis, Egerton). Fins large, with small fulcra. Pectoral fin rays only articulated distally. Dorsal in front of anal fin. Scales small, but thick, obliquely sculptured. 0. ornatus, Eg., from Lower Lias, Lyme Regis. Centrolepis, Egerton. Lower Lias ; Lyme Regis. Atherstonia, Sm. Woodw. Trias (Karoo Formation) ; Colesberg, South Africa. Coccolepis, Ag. Scales thin, rounded, and very deeply overlapping; orna- mented with tubercles. Fulcra minute or absent. Dorsal in front of anal fin. Small species in the Upper Jurassic Lithographic Stone of Bavaria (C. buck- landi, Ag.), the Purbeck Beds and Lower Lias of England. A larger species (C. australis, Sm. AVoodw.) in the Hawkesbury-Wianamatta Formation of New South Wales. Only known Palaeoniscid ranging above the Lias. Cryphiolepis, Traquair. Fins large, with fulcra. Scales large and thin, '8 PISCES CLASS I Lower more or less rounded, very deeply overlapping, and externally striated. Carboniferous ; Scotland. Family -2. Platysomidae. Traquair. Trunk deeply fusiform or irregularly rhombic and laterally compressed. Head hones enamelled; hyomandibular nearly vertical and mouth small; teeth, when present, more or less blunt, chiefly on the pterygoid and splenial bones. Fins with fulcra ; pelvic fins small or absent ; dorsal fin single, much extended. Scales rhombic, deepened on the flank, each with an inner vertical keel projecting as a peg at the upper border. Carboniferous and Permian. Eurynotus, Ag. (Plectrolepis, Ag.). Trunk deeply fusiform. Teeth short, obtusely conical to spher- oidal. Pectoral fins large ; dorsal fin arising opposite the pelvic pair and extending to the caudal fin ; anal fin short- based. E. erenatus, Ag., from Lower Carbonifer- ous, Scotland ; other species from Ireland and Belgium. Mesolepis, Wardichthys, Carboniferous ; and England. Cheirodiis, (Ampltieentrum, (Fig. 140). Trunk deep, rhombic. Pectoral fins very small, pelvic fins absent, Dorsal and anal fins directly opposed, and both Fig. 140. Gheirvdus granulosus. Young sp. Coal Measures ; North Staffordshire. Restored. Lettering as in Fig. 136 (after Traquair). Young ; Traquair. Scotland M'Coy Young), A n Fig. 141. Platysomna striatus. Ag. Upper Permian (Magnesian Limestone); Durham. 1/4 " at - S ' Z,J (restoration alter Traquair). Fig. 14-2. Platysomus parvulus, Ag. Scale, outer (.4), ami innei ( /.') aspects, twice nat. size. Coal Measures ; England. much extended. Teeth absent, but pterygoid and splenial with denticulated sub-class v UAXOIDEI 79 border. 0. granulosus, Young sp. (Fig. 140), from English and Scottish Coal Measures. Other species in Lower Carboniferous, England and Scotland. Cheirodopsis, Traquair. Lower Carboniferous ; Scotland. Platysomus, Ag. (Figs. 141, 142). Trunk deep, rhombic or discoidal. Teeth small, styliform. Pectoral and pelvic fins small. Scales finely striated. P. striatus, Ag. (Fig. 141), from Upper Permian (Marl Slate of England, Kupferschiefer of Germany). Upper and Lower Carboniferous of England and Scotland : Coal Measures of North America ; Permian of Orenburg, Russia. ? Dorypterus, Germar. A scaleless fish, showing internal skeleton. Rare in Upper Permian (Marl Slate of Durham and Kupferschiefer of Germany). Family 3. Catopteridae. Woodward. Trunk elongate or elongate-fusiform; tail abbreviate heterocercal. Head bones ivell developed, ganoid ; no median, series of cranial roof bones ; teeth slender, conical. Dorsal fin single and not much extended. Scales rhombic, ganoid. Trias. Dictyopyge, Egerton. Teeth small. Dorsal opposite or slightly in front of the anal fin. Upper lobe of tail very short ; caudal fin forked. Scales rhombic, smooth or with few oblique furrows. All species small. Upper Trias of England, Germany, Virginia, U.S.A., South Africa, and Australia. Also D. rhenana, Deecke, from Lower Trias (Bunter), near Basle, Switzerland. Catopterus, Redfield (Eedfieldius, Hay). As Dictyopyge, but origin of dorsal behind that of anal fin. Fulcra fine. Trias ; North America. Order 4. LBPIDOSTBI. Huxley. 1 Notochord persistent, or vertebrae in various degrees of ossification. Opercular apparatus usually complete, with branchiostegal rays, and often a gular plate .■ at least one series of postorbitals on the cheekbetween the orbit and preoperculum. Teeth pointed or conical. No infraclavicle. Unpaired, and usually also paired fins fringed with fulcra; supports of dorsal and anal fins equal in number to the dermal rays. i 'ami at fin hemi-heterocercal. Scales rhombic or rhomboidal, arranged in oblique series, and frequently united above and below by peg-and-socket articulations. To the Lepidostei are referred the " bony pikes " at present distributed throughout the fresh waters of North America, besides a large number of fossil genera from Mesozoic formations. Thev are remarkably closelv related to the Palaeoniscidae, and in the ossification of their internal skeleton they represent a higher grade of the same type. Except a single genus from Permian deposits (Acentrophorus), the Lepidosteoids are confined to the Trias, Jurassic, Creta- ceous, and Tertiary, both in Europe and North America. Their maximum development occurs in the Jurassic period. While the Lepidosteoids are closely related on the one hand to the Palaeoniscids, they approach so closely to the Amioids on the other, that it is impossible to separate them distinctly from the latter. . J Egerton, P. M. G., Figures and Descriptions of British Organic Remains (Mem. Geol. Surv. dec. VI., VIII., IX.. XIII.). — Kner, R., Die Fisehe der bituminosen Schiefer von Raibl in Karnthen (Sitzungsb. k. Akad. Wiss. Wien, math.-uaturw. CI. vol. LIII.), 1866 : and Nachtrag, ibid. vol. LV. 1867. — Die fossilen Fisehe der Asphaltschiefer von Seefeld in Tyrol [ibid. vol. L1V.), 1866; and Nachtrag, ibid. vol. LVI. 1867. — Vetter, />'., Die Fisehe ans dem lithographischen Schiefer in Dresilener Museum (Mittheil. k. mineral.-geol. Mus. Dresden), 1881. 80 PISCES CLASS I Family 1. Sty lodontidae. "Wagner. 1 Jaws and vomer with several rows of teeth, those of the outer row styliform. Vertebral column consisting of hemi-vertebrae or ring-vertebrae. All fins fringed with fulcra. Caudal fin both internally and externally hemi-heterocercal, the upper lobe more extensively scaled than the lower lobe. Upper Permian to Upper Jurassic. Acentrophorus, Traq. Trunk fusiform. Dorsal fin short, opposite the space between the pelvic and anal fins. No enlarged ridge scales. A. varians, Kirkby sp., and other species from Magnesian Limestone, Durham. A. chicopensis, Newb. Trias ; Connecticut Valley, U.S.A. Semionotus, Ag. (Ischypterus, Egert.). Trunk fusiform. Dorsal fin large and extended, its hinder part opposed to the anal fin. Dorsal series of pointed ridge scales forming a pro- minent crest. Fin fulcra sometimes very large. Scales and head -bones smooth or but feebly ornamented. S. bergeri, Ag., from Keuper of Coburg and Thuringia. S, hapffi, Fraas (Fig. 143), from Keuper, Haslach, near Stuttgart. Other species from the Bunter, Muschelkalk, Keuper, and Ehaetic of Europe, also from the Upper Karoo Formation of South Africa, the Hawkesbury Formation of New South Wales, and Trias of Connecticut Valley and New Jersey, U.S.A. A Fig. 143. Semionotus kapffi, Fraas. Keuper (Stubensandstein) ; Stuttgart. 2 /3 nat. size (after O. Fraas). -xj=:j Ea^ji'.-^:-;:i; '■■■■'■I ."'V",'<:, ■!l:-fi,. l,-[ir"-}-"l" : l "\^r r i: t :::t --"^Vr Fig. 144. Dapedius pholidotus, Ag. Upper Lias ; Boll, Wurteniberg. V2 na t. size. B, C, Teeth, nat. size (after Quenstedt). Crenilepis, Dames. Muschelkalk. Homoeolepis, Wagner. Upper Lias; Boll. Dapedius, de la Beche (Amblyurus, Ag. ; Aechmodus, Egerton), (Figs. 1 44, - Str'dver, J., Fossile Fische aus dem Keupersandstein von Coburg (Zeitschr. deutsch. geol. Ges. vol. XVI.), 1864. — Wagner, A., Die Griffelzahner (Stylodontes), (Gelehrt. Anzeig. k. bay. Akad. vol. L.), 1860. — Deecke, W., Ueber Fische aus versckiedenen Horizonten der Trias (Palaeoutogr. vol. XXXV.), 1888.— Newberry, J. S., Fossil Fishes and Fossil Plants of the Triassic Rocks (Monogr. U.S. Geol. Surv. vol. XIV.), 1888.— ScMlwien, E., Ueber Semionotus Agassiz (Schriften- Phys.- okon. Gesellsch. Konigsberg), 1901. SUB-CLASS V GAXOIDEI 81 145). Trunk much laterally compressed, deeply fusiform or cycloidal. Ex- ternal bones ornamented with tubercles and ridges of ganoine. Eye surrounded by a complete ring of small quadrangular plates (co), behind which are from five to eight postorbitals (so, cheek- plates). The supra-temporal plates (st) also numerous. Operculum, suboper- culum, and interoperculum large, arranged in an arch. Preoperculum narrow, almost or completely covered by the postorbitals. A median gular plate between the laminar branchiostegal rays. Fin-fulcra A-shaped, the two halves being fused at the apex. Pectoral and pelvic fins small ; dorsal and anal fins much extended and opposed ; caudal fin slightly forked. Scales on the middle of the flank deeper than broad ; no prominent ridge scales ; all the scales thick and enamelled, sometimes tuber- culated. The earliest species in the Alpine Trias (Seefeld, St. Cassian). Common in the Lower Lias of England and the Upper Lias of Wiirtemberg (Boll, Holzmaden), Bavaria (Banz), Fig. 145. Head of Dapedius, ag, Angular; br, ijalai plate; bf, Branchiostegal rays ; d, Clavicle ; co, Circuin- orbitals ; d, Dentary ; /, Frontal ; iop, Interoper- Xorthem France (Calvados), (D. pholi- culum; mx, Maxilla; na, Nasal; op, Operculum; 7 , A ,-. , , /-\ , \ a i or > Orbit; p, Parietal; pmx, Premaxilla ; vt, Post- dOtllS, Ag. j V. CaelatllS, Querist.). AlSO temporal; scl, Supraclavicle ; so, Suborbitals; sop, Suboperculum ; sg, Squamosal ; st, Supratemporal found India. in the Gondwana Beds of (after Traquair). Heterostrophus, Wagner. Lithographic Stone (Upper Jurassic) ; Bavaria. Cleithrolepis, Egerton. Hawkesbury Formation ; New South Wales. Karoo Formation ; Orange River Colony. Tetragonolepis, Bronn (Pleurolepis, Quenst.). Small oval or almost cycloidal fishes, laterally compressed, with small pectoral and pelvic fins. Dorsal and anal fins much extended. Scales deepened on the flank, their front border thickened and forming a vertical ridge. T. semicindus, Bronn, from L^pper Lias, Wiirtemberg and Bavaria. Other species in the Upper Lias of England, and the Kota Formation of the Deccan, India. Family 2. Semionotidae. Woodward. 1 Premaxilla, maxilla, and dentary with obtusely conical or chisel-shaped teeth; vomer, pterygopalatine arch, and splenial with several rows of stouter hemispherical teeth. All fins fringed with fulcra. Caudal fin hemi-heterocercal. Scales thick and rhombic. Trias to Cretaceous. Colobodus, Ag. (Asterodon, Miinst. ; Tholodus, Meyer ; Dactylolepis, Kunisch). Teeth hemispherical and irregularly crowded, usually with a mammiform eleva- 1 Quenstedt, F. A., Ueber Lepidotus in Lias e. Tubingen, 1847. — Sauvage, II. E., Memoire stir les Lepidotus maximus et palliatus (Mem. Soc. geol. France, ser. 3, vol. I.), 1877. — Meyer, H. von. Fossile Fische aus clem Muschelkalk (Palaeontogr. vol. I.), 1850. — Dames, W., Die Ganoiden des deutschen Muschelkalks (Palaeont. Abhandl. vol. IV.), 1888. — Branco, W., Ueber eine neue Lepidotus- Art aus dem Wealden (Jalirb. VOL. II preuss. geol. Lahidesanst.), 1885. G 82 PISCES CLASS I tion in the middle of the crown. Scales marked with more or less parallel ridges, ending in denticulations at the hinder border. Common in the Muschelkalk and Lettenkohle. The generic names Nephrotus, Cenchrodus, Omphalodus, Hemilopas, Meyer, and Sargodon, Plieninger (Fig. 146), are applied to rounded or chisel-shaped teeth from the Trias and Rhaetic. Lepidotus, Ag. (Sphaerodus, p.p. Ag. ; Plesiodus, Wagner ; Prolepidotus, Michael), (Figs. 147, 148). Trunk fusiform and only moderately compressed, covered with thick, smooth, or obliquely striated scales, which are deeply imbricating and have the angles of the overlapped border more or less produced. Head and opercular bones more or less enamelled, smooth or tuberculated. Teeth hemispherical to obtusely conical. Successional teeth numerous, the incipient germ lying exactly in the opposite direction to that of the functional tooth, thus making a revolution of 180° while the root of the old tooth is absorbed and it prepares to appear Fig. 14(3. Surgodon tomicus, Plien. Rhaetic ; Kem- nath, Wiirtemberg. l-'i.i. 147. Lepidotus notopterus, Ag. Upper .Jurassic Lithographic Stone) ; Solenhofen. V 5 nat. size. (Fig. 148, A). Fin fulcra very large and biserial (Fig. 148, D), present on all the fins. Pectoral fins large ; pelvic fins small ; large dorsal fin opposed to the pelvic pair ; caudal fin more or less forked. Ranging from the Keuper Fig. 14S. Lepidotus. A, Fragment of jaw with successional teeth. B, Tooth in side view and from above. C, Scale. I), Federal armature of dorsal fin. /, Fulcra ; x, Unpaired dorsal scale ; y, First basal scale of dorsal fin ; z, .:'. lateral scales. Nat. size. to the Lower Cretaceous, some of the later species having the largest, stoutest teeth and well-developed ring-vertebrae. The type species, L. elvensis, Blv. sp., common in the Upper Lias of Wiirtemberg, Bavaria, France, and England. L. maximus, Wagn., L. notopteri^ Ag. (Fig. 147), and other species well pre- SUB-CLASS V GANOIDEI 83 served in the Lithographic Stone (Upper Jurassic) of Germany and France. L. mantelli, Ag., from \Yealden. Also Jurassic of India and Siberia, and Cretaceous of Brazil. Family 3. Eugnathidae. Woodward. Trunk slender, covered with rhomboid enamelled scales. Marginal teeth conical. Cranial and facial bones moderately robust, externally enamelled, and opercular apparatus complete. Snout not produced. Fin- rays robust, fulcra conspicuous. Dorsal fin short and acuminate. Vertebral column rarely more than incomplete rings. Tail externally homocercal or hemi-heterocercal. Trias to Cretaceous. Eugnathus, Ag. (Heterolepidotus, Egerton). Cleft of mouth wide, with large, conical, pointed laniary teeth and numerous smaller pointed teeth between these. Head and opercular bones smooth or tuberculated. Fins powerful, the dorsal arising opposite the pelvic pair, stouter and longer than the anal tin; caudal fin forked, externally hemi-heterocercal. Scales rather thick, mostly longer than deep, and with serrated hinder border. The type species, E. orthostomus, Ag., a slender fish, common in the Lower Lias of Lyme Eegis, Dorset. Other species in the Lias, and ranging upwards to the Lithographic Stone (E. microlepidotus, Ag.) and Purbeck Beds. Caturus, Ag. (Uraeus, Ag.), (Fig. 149). Essentially identical with Eugnathus, but scales thinner, more deeply overlapping, and less narrowed near the ventral Pig. 149. Caturus elongatug, Ag. Upper Jurassic (Lithographic Stone) ; Cerin, Ain, France. ' '•_. aat. size. border of the fish. Endoskeleton of trunk usually well displayed in the fossils, showing hemi- vertebrae, short ribs, and free neural spines in the abdominal region. Ranging from the Trias to the Upper Jurassic, especially fine speci- mens being known from the Lower Lias of England (C. hetenurus, Ag. sp., etc.), and the Lithographic Stone of France, Bavaria, and Wurtemberg (0. furcatus, elongatus, maximus, Ag., etc.). Strobilod'us, Wagner; Ditaxiodus, Chven. Large fishes resembling Caturus. Upper Jurassic of Europe. Callopterus, Thiolliere. Lithographic Stone of Bavaria and France. Euryrnrmiis, AVagner (Fig. 122). Much resembling Caturus, but vertebral column consisting of hemi-vertebrae, which become two similar complete rings in the caudal region. Dentition comparatively feeble. E. speciosus, Wagn., from Lithographic Stone, Bavaria. Other species in Oxford and Kimmeridge Clays, England. 84 PISCES CLASS I Ptycholepis, Ag. Head and opercular bones ornamented with ridges of ganoine ; teeth minute. Scales thick, much longer than deep, externally marked with longitudinal grooves. P. bollensis, Ag., from Upper Lias of England, France, Bavaria, and Wiirtemberg. Other species in Lower Lias of England. Smaller species in Trias of Raibl, Carinthia, and Connecticut. extending Family 4. Macrosemiidae. Marginal teeth styliform ; dorsal fin elongated ; scales rhombic. Ophiopsis, Ag. Trunk much elongated and slender, with a high dorsal fin half its length. Anal fin small. Caudal fin hemi-heterocercal. Ranging from the Muschelkalk to the Purbeck Beds. 0. procera, Ag., and other species common in the Lithographic Stone of Bavaria. Macrepistius, Cope. Lower Cretaceous ; Texas. Eusemius, Vetter. Upper Jura ; Bavaria. Notagogus, Ag. Trunk elongated, with extended dorsal fin subdivided into two parts, the anterior portion with comparatively widely spaced rays, and not deeper than the posterior portion. Stout ring-vertebrae. N. penilandi, Ag., from Neocomian, Castellamare, near Naples. Other species in the Lithographic Stone of Bavaria. Propterus, Ag. As Notagogus, but trunk deeper and anterior portion of dorsal fin deeper than posterior portion. Ring-vertebrae. Scales almost six-sided, deeper than long. Jura. Histionotus, Egerton. The back of the elongated trunk elevated and sharply bent anteriorly, a single long dorsal fin extend- ing backwards from the bend almost to the caudal fin, which is deeply forked. Uniserial fulcra on both paired and median fins. Scales of flank deeper than broad. H. angularis, Eg., from the English Purbeck Beds. Other species from the Lithographic Stone of Bavaria and France. Macrosemius, Ag. (Disticholepis, Thioll.), (Fig. 150). Trunk elongated, and dorsal fin extending from the occiput to the caudal fin, which is rounded. No fin fulcra. Jaws and pterygoid with power- ful conical or styliform teeth. Scales thin and rhombic. M. rostratus, Ag., M. latiusculus, Wagn. (Fig. 150), and other species in the Lithographic Stone of Bavaria and France. Small species of this or an allied genus in the Purbeck Beds of Wiltshire and the Portlandian of Meuse, France. Petalopteryx, Pictet. Upper Cretaceous ; Mount Lebanon. Fig. ]50. , nat. size. Kelheim . Macrosemius latiusculus, Wagn. Hea Upper Jurassic (Lithographic Stone) : ar, Articular ; br, Branchiostegal rays ; cl, Clavicle ; d, Dentary ; hy, Ceratohyal ; mx, Maxilla ; o, Orbit ; op, Operculum ; pa, Parietal ; pi, Palatine ; pmx, Premaxilla ; pop, Preoperculum ; psph, Para- sphenoid ; pt, Pterygoid ; qu, Quadrate ; sop, Sub- operculum ; spl, Splenial ; vo, Vomer. Family 5. Pholidophoridae. Trunk fusiform ; teeth small and conical; scales rhombic and deeply overlapping ; dorsal and anal fins small ; vertebrae forming complete rings. Pholidopleurus, Bronn (Fig. 151). Trunk slender. Scales smooth, one SUB-CLASS V (iAXOIDEI 85 Fig. 151. I'holidopleurus typus, Bronn. Keuper ; Raibl, Carinthia. 2/3 nat. size (after Kner). series short and very deep on the flank, those on the back and ventral region longer than deep. Dorsal and anal fins delicate, elongated, and low, directly opposed on the hinder part of the caudal region. Caudal fin ex- ternally homocercal, slightly forked. Trias ; Raibl, Carinthia. Pleuropholis, Egerton. Upper Jurassic (English Purbeck Beds, and French and Bavarian Lithographic Stone). P. egertoni, Wagn. Pholidophorus, Ag. (Figs. 152, 153). Body shaped like a carp. Scales thin, deeper than long on the flank, en- amelled, smooth or finely striated and serrated. Small dorsal fin opposed to the pelvic pair. Caudal fin externally homocercal, deeply forked ; • a large, unpaired dorsal scale often at its base. Com- mon in the Alpine Trias of Raibl (P. bronni, Kner) and Seefeld ; in the Lias of Lyme Regis (P. bechei, Ag., P. lim- batus, Ag.), Whitby, Cal- vados, Wur- temberg, and Bavaria (P. germ aniens, Querist.) ; in the Lithogra- phic Stone of Bavaria and France ; in the Purbeck Beds of England and Lower Jura of the Black Hills, South Dakota. Isopholis, Zittel. As Pholidophorus, but scales of equal size and rhombic. Pectoral and anal fins large. Lithographic Stone of Bavaria and France. ii«. PJiolidophorus striolaris, Ag. Head, nat. size. Upper Jurassic (Lithographic Stone) ; Eichstadt. cl, Clavicle ; jr., Frontal ; iop, Interoperculum ; mil, Mandible ; mx, Maxilla ; na, Nasal ; op, Operculum ; pa, Parietal ; pmx, Preniaxilla ; pop, Preoperculum ; psp/i/Parasphenoid ; pt, Post-temporal ; sd, Supraclavicle ; so, Suborbitals ; sop, Suboperculum. Fig. 153. Pholidophorus ptisillus, Ag. Rhaetic ; Seefeld, Tyrol. Nat. size. Faniilv 6. Pycnodontidae. Agassiz. Trunk laterally compressed, very deep, oval. Notochord persistent. Bibs, vertebral arches, and spines well ossified. Opercular apparatus incomplete, mill one or two h'anchiostegal rays. Premaxilla with two to four prehensile front teeth; maxilla thin, deepened behind, toothless ; palatine and vomerine bones fused together, •usually with five longitudinal series of round or oval grinding teeth ; splenial of mandible large, with coronoid p>rocess, and three, four, five, or more rows of grinding teeth ; dentary small and terminal, fitting in a groove of the splenial, "ml bearing two to four prehensile front teeth. Branchial arches with very numerous, closely arranged, bony filaments. Clavicle broadly ovate at the lower end. Fin fulcra absent. Pelvic fins small. Dorsal and anal fins much extended. Scales deeper than long, with a thickened, ridge-like anterior margin. Lower Lias to Upper Eocene. Gyrodus, Ag. (Figs. 154-157). Trunk completely covered w T ith scales. 86 PISCES CLASS I Frontal profile steep. Vomero-palatine with five rows of rounded, bean-shaped teeth, of which the convex crown has a rugose border and mammillated apex ; the middle row larger than the lateral rows. Splenial with four rows of similar teeth ; dentary with three stout prehensile teeth. Caudal fin deeply forked, symmetrical. Common in the Upper Jurassic (Lithographic Stone) of Solenhofen, Eichstad't, Kelheim, Cerin (Ain) ; also in the Kimmeridgian of England, France, and Switzerland, in the Portlandian and Neocomian of Fig. 155. Gyrodus ttfaniiis, Wagn. Scale, inner (^4) and outer (/») aspects, nat. size. Kelheim. pmx> Fig. 154. Head of Gyrodus macrophtlialmus, Ag. Upper Jurassic (Lithographic Stone) ; Kelheim, Bavaria, c, Slime canals ; cl, Clavicle ; eth, Ethmoid ; fr, Frontal ; md, Mandible ; mx, Maxilla; 0, Orbit; op, Preoperculum ; pa. Parietal; pfr, Post-frontal; pmx, Premaxilla ; pt, Post - temporals ; sc, Sclerotic ring ; scl, Operculum ; sq, Squamosal. France and Switzerland, and the Tithonian of Sicily. Some species from the Litho- graphic Stone (G. titanius, Wagner) attain a length and depth of 1 m. Microdot, Ag. (Figs. 158, 159). Hinder half of trunk with very thin scales, which are often wanting. Vomero-palatine slender, with five rows of quadrate, smooth, and flattened teeth ; between the large teeth of the middle row the smaller teeth of the two inner lateral rows are alternately pressed inwards. Splenial with one row of large, obliquely quadrate, smooth teeth, which is flanked inside by one, outside by two rows of smaller teeth. Caudal fin slightly forked, symmetrical. Common in the Upper Jurassic (Lithographic Fig. 156. Gyrodus titan ins. Wagn. Palatal plate with teeth, nat. size. Kelheim. Fig. 157. Gyrodus titani us, Wagn. Right splenial with four rows of teeth, nat. size. Upper Jura ; Kelheim. SUB-CLASS V GANOIDEI 87 Stone) of Bavaria and France, and in the Purbeck Beds of England. Earliest Fig: 158. Microdon wagneri, Thiolliere. Upper .Jurassic ; Cerin, Ain, France. i/ 3 nat. size (alter Thiolliere). fragments in the Stonesfield Slate (Bathonian), Oxfordshire. Also Corallian and Kimmeridgian, Hanover and Switzerland. Mesodon, Wagner. As Microdon, but teeth on vomero- palatine in five Fig. 159. Microdon elegans, Ag. Vomeropalatine (A), splenials of mandible (B), and anterior teeth of mandible, inner view (C), and outer view (D), nat. size. Upper Jurassic ; Kelheim. Fig. 160. Anomoeodus muensteri, Ag. sp. Man- dibular (splenial) teetli (A), and vomero- palatine teeth, oral aspect (/>'). and side view ('), nat. size. Greensand ; Kelheim. regular rows, and the large* teeth on splenial flanked by three or four irregular rows of smaller teeth. Caudal fin rounded behind, not excavated. M. liassicus, Egert. sp.j from the Lower Lias of England, is the oldest known Pycnodont, the 88 PISCES class i genus ranging upwards to the Lower Cretaceous both in Europe and North America. Fine specimens in the Lithographic Stone of Bavaria and France. Mesturus, Wagner. 1 Much resembling Gyrodus, but with more irregular teeth, rounded caudal fin, and scales often united above and below by jagged sutures. M. verrucosus, Wagn., from Lithographic Stone of Bavaria. M. leedsi, Sm. Woodw., represented by fine specimens displaying osteology from Oxford Clay, Peterborough. Stemmatodus, Heckel. Small, resembling Microdon. Vomero-palatine teeth in five, splenial in three rows, all teeth rounded and not very unequal in' size. Lower Cretaceous ; Castellamare. Coelodus, Heckel. Hinder half of trunk scaleless. Yomero-palatine teeth with one median row of large, transversely elongated, smooth, oval teeth, and two lateral rows of small teeth. One row in the splenial dentition relatively very large, its teeth transversely elongated. Caudal fin either slightly ex- cavated or convex mesially and slightly hollowed laterally. Lower Cretaceous of Istria, Dalmatia, Southern Italy, and England ; also Cenomanian and Turonian in Europe and North America. Anomoeodus, Forir (Fig. 160). Vomero-palatine teeth in three or five longitudinal series, more or less irregular. Splenial dentition with one row relatively large, the lateral series more or less irregular, and not reaching the oral border of the bone. A. subclavatus, Ag. sp., from Upper Cretaceous, Maestricht. A. muensteri, Ag. sp., and other species from the European Greensand. Also North America. Palaeobalistuni, Blv. Upper Cretaceous ; Europe, Asia, and Brazil. Upper Eocene ; Monte Bolca. Pycnodus, Ag. Trunk rather elongated, with slender caudal pedicle and forked caudal fin. Dorsal much more extended than the anal fin. Scales thin, absent on the caudal region. Teeth of the three middle rows of the vomero-palatine rounded, those of the two outer rows somewhat smaller and elliptical. P. platessus, Blv. sp., from Upper Eocene ; Monte Bolca. Dentition in the Eocene of several European localities. P. moJcattameusis, Priem, from Eocene, Mokattam Hills, Egypt. Family 7. Aspidorhynchidae. Woodward. 2 Very slender, elongated fishes, with enamelled rhomboid scales of different sizes. Snout beak-like, elongated, and pointed. Maxilla loose ; mandible with a movable praemandibula (" presymphysial bone''). Teeth conical, pointed. Branchiostegal rays numerous. Notochord with ring -vertebrae. Caudal fin externally homocercal. Fin fulcra minute. Bathonian to Upper Cretaceous, Aspidorhynchus, Ag. (Fig. 161). Thin, slender fishes, attaining a metre in length, with enamelled ganoid scales, which are yellow or brown in colour, more or less rugose externally, and not remarkably thick. Pectoral fin with very broad rays, which are jointed only in their distal quarter ; no fulcra. Pelvic fin somewhat behind the middle point of the trunk. Anal fin opposed to the small dorsal fin. Caudal fin deeply forked, with delicate fulcra. Lower jaw much shorter than the snout, which is formed by the mesethmoid and pre- 1 Woodward, A. S., Ann. Mag. Nat. Hist. ser. 6, vol. XVII. 1896, p. 1. - Reis, 0., Ueber Asjndorhyachus, Belonostomus, mid Lepidosteus (Sitzungsb. k. bay. Akad. Wiss:, matb.-pbys. CI.), 1887. * SUB-CLASS V GAXOIDEI 89 maxillae. The oldest known species is A. crassus, Sin. Wood., from the Stonesfield Slate (Bathonian) of Oxfordshire. Well-preserved fishes in the Lithographic Stone of Bavaria (A. acutirostris, Blv. sp.) and France; also in the English Purbeck Beds (A. fisher i, Egerton). Belonostomus, Ag. As above, but mandible almost as long as the snout. Kimmeridgian to Upper Cretaceous. Fine skeletons in the Lithographic DTTld Fig. 161. Aspidorhynchus acutirostris, Ag. Upper Jurassic ; Solenhofen. iop, Interoperculuni ; md, Mandible; mx, Maxilla; op, Operculum; pmd, Predentary ; pop, Preoperculum ; pt, Pterygoid; qy,, Quadrate; ;■;, Hinder cheek-plate ; so, Suborbitals ; sop, Suboperculum. Stone of Bavaria (B. split/ raenoides, Ag., etc.) and the Cretaceous of Europe, India, Brazil, and Queensland. Family 8. Lepidosteidae. Bony pikes. 1 Trunk elongated, with thick, enamelled rhombic scales. Snout much produced, the very long maxilla divided by a series of vertical sutures into several pieces, which bear large pointed laniary teeth and small clustered teeth ; premaxilla short and toothed. Vomer double. Vertebral column completely ossified, bent upwards into the superior lobe of the tail; vertebrae opisthocoelous. All fins with biserial fulcra. Dorsal and anal fins very remote, near the hemi-heterocercal, rounded caudal fin. Tertiary and Recent. Lepidosteus, the only genus of this family, survives in the rivers of the southern United States, Central America, and Cuba. Complete individuals occur also in the Eocene and Lower Miocene of Europe and North America. L. atrox, Leidy, from the Middle Eocene Green River Shales of Wyoming, attains a length of 1*7 m. Order 5. AMIOIDEI. Liitken. Notochord persistent, or vertebrae in various degrees of ossification. Opercular apparatus always complete, with larnelliform branchiostegal rays and a welldereloped gular plate. Teeth pointed or conical. No infraclavicle. Fulcra present or absent. Supports of dorsal and anal fins equal in number to the dermal rays. Caudal fin hemi- heterocercal. Scales very thin, overlapping, rounded or rhombic at the hinder border. The Amioids are distinguished from the Lepidostei by their thin, cycloid or rhombic scales, which are not articulated with each other, but merely 1 Eastman, C. R., Fossil Lepidosteids from the Green River Shales of Wyoming (Bull. Mus. Comp. Zool. vol. XXXVI. p. 67), 1900. Also Geol. Mag. [4] vol. VII. p. 54, 1900. 90 PISCES CLASS I overlap. Notwithstanding their thinness, however, the scales exhibit the characteristic structure of true ganoid scales ; the base contains bone cells, the surface is covered with enamel. In many Jurassic genera the vertebral column consists of hem i- vertebrae or complete rings, but it is also often completely ossified. Contrary to the arrangement in certain closely related bony fishes (Physostomi), the terminal vertebrae are continued some distance into the upper lobe of the tail. Only one genus (Amia) still survives in the rivers of the southern United States and Central America. The order ranges upwards from the Upper Lias. Fig. 162. Family 1. Pachycormidae. Doderlem. (Microlepidoti and Cyclolepidoti, Zittel.) Vertebral axis with very numerous segments, with or without hemi- vertebrae. Ethmoid forming a prominent rostrum. Branchiostegal rays very numerous (thirty to forty). Neural spines in abdominal region separate from arches. Caudal fin deeply forked, powerful, only infernally heterocercal. Teeth laterally compressed, lanciform, in two series, the largest of which are set in alveoli, Upper Lias to Upper Cretaceous. Pachycormus, Ag. Large, salmon- shaped fishes, with hemi-vertebrae only Euthy't micropodius, Ag.sp. Upper i in t ^ e cau d a l reeion. Operculum, sub- Wurtemberg. A, Vertebrae (c, Haemal arches; hyc, o r Hypocentrum ; n, Neural arches ; p, Parapophyses ; operculum, and Suborbitals Vdy large. pic, Pleurocentrum ; sp .Neural spine). B, Scales. -.^T P ,, ., n -^.i j- Rays of all the fins with distant articulations. Pectoral fins large ; pelvic fins absent ; short dorsal fin arising in front of the anal ; deeply forked caudal with elongated 7 nj N f / y y j j jj /^ fulcra on each lobe. P. macropterns, Blv. sp., and other species in the Upper Lias of Germany, France, and England. Euthynotus, Wagner (Heterothrissops, Pseudo- thrissops, Sauvage), (Fig. 162). Hemi-vertebrae pre- sent. Fin fulcra minute. Pelvic fins present ; dorsal fin opposed to much ex- tended anal fin. Scales rhombic, rounded at the angles. E. speciosus, Wagn., and other species in the Upper Lias of Germany and France. Hyp s o corm u s, W a g n e r (Fig. 163). Large fishes, with very small rhombic scales, much resembling IMP* Fig. 163. Hypsocormus insignis, Wagn. Portion of trunk. Upper Jurassic (Lithographic Stone) ; Eichstadt, Bavaria. SUB-CLASS V GAXOIDEI 91 Pachycormus, but with larger teeth, small pelvic fins, and a much extended anal fin. Large teeth rounded in section, of complex structure. H. insignis, Wagn., from Lithographic Stone of Bavaria. H. leedsi, Sm. Woodw., from Oxford Clay, Peterborough. Protosphyraena, Leidy 1 (Erisichthe, Pelecopterus, Cope), (Fig. 164). Known only by fragments of head and fins much resembling those of Hypsocormus, but teeth laterally compressed, and snout more produced. P. ferox, Leidy, and other species, in the Upper Cretaceous of Europe and North America. The teeth were wrongly ascribed to Sauro- cephalus, Harlan, by Agassiz. (Megaluridae, Zittel ; Halecomorphi, Cope.) Family 2. Amiidae. Giinther. Fin. 164. Tooth of Proto- sphyraenaferox,lie\>\ y. Vertebral column well ossified, and flexed upwards behind into Upper chalk ; Maes- the upper part of the rounded caudal fin. Pleurocentra and hypo- centra forming complete alternating discs in part of the caudal region, the alternate discs bearing the neural and haemal arches. Teeth powerful. Branchiostegal rays broad and few ; gular plate large. Fulcra present or absent. Scales very thin and cycloid. Upper Jurassic to Recent. Megalurus, Ag. (Figs. 165, 166). Vertebral column much produced into Fig. 165. Megalurus i legantissimus, Wagn. Upper Jurassic ; Solenhofen, Bavaria. 2/3 nat. size. 7; Fig. 166. Megalurus polyspondylus, Miinst. Upper Jurassic; Kelheiin. A, Portion of vertebral column, nat. size. B, Scales, enlarged. Fig. 167. A in in calva, Linn. Head, from !>!•- neath. Recent; South Carolina, brs, Branchiostegal rays; h, Ceratohyal; jug, Gular plate ; mil, Mandible the upper caudal lobe ; caudal hemi- vertebrae rather elongated. Fulcra present. Dorsal fin considerably extended, arising opposite the pelvic fins, 1 Felix, J., Zeitschr. deutsch. geol. Ges. vol. XLII. 1890, p. 278. — Woodward, A. S?n.. Ann. Mag. Xat. Hist. ser. 6, vol. XIII. 1894, p. 510. 92 PISCES CLASS I and reaching the hinder end of the anal fin ; caudal fin convex behind, very large. Several species in the Upper Jurassic (Lithographic Stone) of Bavaria, Nusplingen, and Cerin, and in the English Purbeck Beds. M. mawsoni, Sm. Woodw. From Cretaceous of Bahia, Brazil. Liodesmus, Wag. (Lophiurus, Vetter). Lithographic Stone ; Bavaria. Opsigonus, Kramberger ; Amiopsis, Kner. Lower Jura ; South Dakota. Lower Cretaceous ; Dalmatia and Istria. Amia, Linn. (Cyclurus, Notaeus, Ag.), (Fig. 167). Fulcra absent. Dorsal fin arising in front of the pelvic pair and extending to the caudal fin. Living in North America ; fossil in the Upper Eocene and Lower Miocene freshwater formations of Europe and North America. A. (Notaeus) longicauda, Ag. (Montmartre), A. (Cyclurus) valenciennesi, Ag. (Armissan), A. kehreri, Andreae (Messel, near Darmstadt), A. anglica, Newton (Isle of Wight). Pappichfhys, Cope. Eocene ; North America. Family 3. Oligopleuridae. Smith Woodward. Vertebrae well ossified, with no distinct pleurocentra and hypocentra. Mouth wide, with teeth small or of moderate size. Fulcra present. Scales very thin and cycloid. Upper Jurassic to Upper Cretaceous. Oligopleurus, Thiolliere (Fig. 168). Teeth very small, and mandible prominent. Vertebral centra not pitted. Dorsal fin short-based, opposed to Fig. 168. Oligopleurus esocinus, Thioll. Upper Jurassic (Lithographic Stone) ; Cerin, Ain, France. V4 nat. size (after Thiolliere). anal fin. Caudal fin slightly forked. Scales rather large. 0. esocinus, Thioll., from Lithographic Stone, Cerin (Ain, France). Other species in English Wealden and Purbeck Beds. Oenoscopus, Costa (Attakeopsis, Thioll. ; Macrorhipis, Wagn.). Almost as above, but vertebral centra with two lateral pits, and greater portion of dorsal in advance of anal fin. 0. petraroiae, Costa, from Lower Cretaceous, Pietraroja, Prov. Benevento, Italy. Other species in French and German Lithographic Stone. Spathiurus, Davis. With much extended dorsal fin. Upper Cretaceous ; Mount Lebanon. Sub-Class 6. TELEOSTEI. 1 Bony fishes. Skin with thin, elastic, cycloid or ctenoid scales, rarely with bony plates. Vertebral column ossified ; tail internally and externally homocercal. Intermuscular bones more 1 Bassani, Fr., Descrizioue clei pesci fossili di Lesina accompagiiata da appunti sn alcune altre ittiofaune cretacee (Denkschr. k. Akad. Wiss. Wien, math.-naturw. CI. vol. XLV.), 1882.— Kner, R., Ueber einige fossile Fische aus Kreide und Tertiarschichten von Comen und Podsuded (Sitzungsb. sub-class vi TELEOSTEI 93 or less numerous. Fin fulcra absent. In the living for ins — optic nerves completely decussating, conns arteriosus of the heart with only two valves, and intestine without a spiral valve. The distinction between the bony fishes and ganoids consists parti v in the dermal skeleton and partly in anatomical characters, which cannot usually be verified by palaeontologists. The two sub-classes are most closely related to each other, and the line of demarcation between the Amioidei and the Physo- stomi is often almost obliterated. This applies specially to the scales, which have already become thin and elastic in the former, and are not distinguishable in any respect from those of certain Physostomi, in which a thin calcified layer with bone cells happens to be developed beneath the outer smooth layer. Among Teleostei the internal skeleton is often characterised by its very dense structure and the sparse development of bone cells. The caudal fin, unlike that of the ganoids, is usually both internally and externally homocercal. In the more specialised forms the pelvic fins are sometimes displaced far forwards, while the rays of the dorsal fins are sometimes articulated, sometimes spinous. The Teleostei are divided into the two orders of Physostomi and Physoclysti. Order 1. PHYSOSTOMI. Miiller. Air bladder, when present, connected by a tube with the oesophagus. Pelvic fins abdominal ; all. fin rays articulated, except the foremost rays of the pectoral and dorsal fins, which are sometimes spinous. Scales, when present, usually cycloid. Of all the bony fishes the Physostomi approach most closely the ganoids, especially the Amioidei. They probably originated from the latter in the Trias, becoming specialised in their own line, and soon considerably exceeding their ancestors in diversity of form. They already exhibit an important develop- ment in the Upper Jurassic and Lower Cretaceous, but attain their widest distribution in the Tertiary and at the present day. They live partly in the sea, partly in fresh-waters. Family 1. Leptolepidae. Smith Woodward. Trunk elegantly fusiform. Head with delicate membrane bones and well-developed cheek plates, more or less enamelled ; parietals meeting in middle line, flanked by large squamosals ; premaxilla very small ; maxilla large, entering the gape, loosely attached and with two supramaxillaries ; teeth small and conical. Opercular apparatus complete. A single dorsal fin. Scales ganoid and with bony layer. Upper Lias to Lower Cretaceous. Leptolepis, Ag. (Tharsis, Giebel), (Figs. 169, 170). Usually small fishes. Dorsal fin in front of anal fin, which is not much extended. Dentary bone sharply rising into a thickened obtuse elevation near its anterior end. Teeth k. Akad. Wiss. Wien, math.-naturw. CI. vols. XLVIIL, LYI.).—Kner and Steindachaer, Neue Beitrage zur Kenntniss der fossilen Fische Oesterreichs (Denkschr. Akad. Wien, vol. XXL), 1863. — Kramberger, D. G., Die eocanen Fische der Baschker Schichten (Palaeontogr. vol. XXIV.). — Die jungtertiare Fischfauna Croatiens, I., II. (Beitr. Palaeont. Oesterr.-Ungarns, vols. II., III.), 1882-83. —Meyer, H. v., Palaeontogr. vols. II., VI. — Sauvage, II. E., Bull. Soc. geol. France, ser. 3, vols. II., III., VI., XI. — Steindachner, F., Beitrage zur Kenntniss der fossilen Fischfauna Oesterreichs, I. -IV. (Sitzungsb. Akad. Wien, vols. XXXVII., XXXVIII., XL., XLVIL), 1859-63. — Wettstein, A., Ueber die Fischfauna des tertiaren Glarnerschiefers (Abh. schweiz. palaeont. Ges. vol. XIII. ), 1886. 94 PISCES CLASS I minute. L. bronni, Ag., and other comparatively small species in the Upper Lias of England, France, and Germany. L. dubius, Blv. sp., L. sprattiformis, Ag. (Fig. 170), and other species in the Upper Jurassic (Lithographic Stone) Fig. 169. Head of Leptolepis Icnorri, Ag. Upper Jurassic ; Kelheim. Reduced. Fig. 170. Leptolepis sprattiformis, Ag. Upper Jurassic ; Eichstadt, Bavaria. Xat. size. of Bavaria and France ; also from the English Purbeck Beds, the Lower Cretaceous of the Isle of Lesina, Dalmatia, and the Wianamatta Formation of New South Wales. Fragments from King Charles Land, Spitzbergen. Thrissops, Ag. Sometimes attaining rather large size. The short dorsal fin opposed to the much extended anal fin. Ribs very stout. Upper Jurassic and Lower Cretaceous of Europe, the type species being T. formosus, Ag., from the Bavarian Lithographic Stone. Aethalion, Minister. Lithographic Stone ; Bavaria. Family 2. Elopidae. Trunk fusiform, and caudal region relatively short. Head with well-developed cheek plates, not enamelled ; jaws as in Clupeidae. Opercular apparatus complete, with numerous branchiostegal rays, and usually a gular plate. A single dorsal fin, without adipose dorsal. Scales thin and cycloid, without bony layer. Lower Cretaceous to Recent. Elopopsis, Heckel. Gape of mouth wide, with large teeth. E. fenzli, Heckel, from Neocomian, Comen, Istria. E. ziegleri, v. d. Marck, and other species in the Upper Cretaceous of Europe. Osmeroides, Ag. (Bhabdolepis, v. d. Marck non Troschel ; Holcolepis, v. d. Marck). Salmon-shaped fishes with minute clustered teeth, and very deeply overlapping scales. 0. lewesiensis, Mantell sp., from English Chalk. Other species in the Upper Cretaceous of Westphalia and Mount Lebanon. Thrissopater, Giinther. Gault ; Folkestone. Pachyrhizodus, Dixon (Hypsodon, Ag.). Upper Cretaceous ; Europe and North America. Bhacolepis, Ag. Upper Cretaceous ; Brazil. Megalops, Lacep. ; Elops, Linn. Eocene to Recent. Family 3. Albulidae. Clupeoids with very small mouth, and some inner bones with grinding teeth. Branchiostegal rays few, and gular plate absent. Upper Cretaceous to Recent. Istieus, Ag. An elongate fish, with much extended dorsal fin, small anal fin, and forked tail. Teeth very small. Closely resembling the existing deep- sea fish, Bathythrissa, Giinther. About three species in the Upper Cretaceous of Westphalia and Syria. SUB-CLASS VI TELEOSTEI 95 Pisodus, Owen. Large hemispherical or flattened crushing teeth on the parasphenoid. Closely resembling existing Albula. Lower and Middle Eocene of England and Belgium. Family 4. Ichthyodectidae. Crook. 1 Large extinct predaceo us fishes, with a row of strong conical teeth fixed in sockets on the margin of the jaws. Upper jaw formed by short and deep premaxilla, and long stout maxilla ; mandible deep, truncated in front, without any presymphysial bone. Vomer and parasphenoid toothless; palato-pterygoid arch with patches of small teeth. Paired fins composed of a very broad, anterior, and numerous narrower rays, finely divided and articulated quite at the distal end. Dorsal fin short ami remote; anal fin not much extended ; candid fin forked. Cretaceous. This family is very closely related to the existing Chirocentridae, of which only one genus (Chiro- centrus) is known, in- habiting the Indian Ocean. Portheus, Cope {Xiphactinus, Leidy ; Hupsodon, Ag. p.p.), (Fig. 171). Powerful fishes, sometimes of gigantic size. Teeth of variable size, oval in transverse section. Palatine movably articulated with eth- moid, with hammer- shaped thickening. Eye with ossified sclerotic ; three sub- orbital plates. Oper- culum well developed and large. P. molossus, Cope (Fig. 171), and other species occur in the Chalk of Kansas, U.S.A. P. mantelli, Newton, and other species in the Chalk and Gault of England, France, Belgium, Bohemia, and Saxony. Fragments also in Cretaceous of Rolling Downs, Queensland. Ichthyodedes, Cope. As Portheus, but smaller, and teeth of uniform size. Chalk of Kansas and England. Gillicus, Hay. Like the preceding, but teeth small and fringe-like. Upper Cretaceous ; Kansas. Spathodactylus, Pictet. Type specimen displaying fins. Xcocomian ; Voirons, Switzerland. 1 Crook, A. It., Ueber einige Knoclientische aus der niittleren Kreide von Kansas (Palaeontogr. vol. XXXIX.), 1892.- — Loom is, F. B., Die Anatoniie und die Verwandtschaft der Ganoid und Knocheutisehe aus der Kreide von Kansas (Palaeontogr. vol. XLVI.), 1900. — Stewart, A.. Teleosts of the Upper Cretaceous (Univ. Geol. Surv. Kansas, vol. VI.), 1900. Fig. 171. Head of Portheus molossus, Cope. Niobrara Cretaceous ; Fox Caiion, Kansas. ] 4 nat. size (after Cope). 96 PISCES CLASS I Family 5. Saurodontidae. Cope (non Zittel). Skull laterally compressed ; jaws powerful, and bearing a single row of compressed, knife-like teeth, with nutrient foramina or notches below the internal alveolar border ; a presymjjhysial bone present and without teeth. Cretaceous. The two genera constituting this family, Saurocephalus, Harlan (non Ag.), and Saurodon, Hays (Daptinus, Cope), differ from the Ichthyodectidae in the presence of a presymphysial bone and in the form and manner of succession of teeth. In the first-named genus the crowns of the teeth are short and compressed, with nutrient foramina below the alveolar border on the inner face of the jaw ; and in Saurodon the inner margin of each dental alveolus is deeply notched. Upper Cretaceous ; New Jersey and Kansas. Family 6. Clupeidae. Herrings. Trunk elegantly fusiform. Supraoccipital bone separating parietals, and otic region prominent; cheek plates reduced; premaxilla very small; maxilla large, entering the gape, with two supramaxillaries ; dentition feeble. Opercular apparatus complete, but few branchiostegal rays, and no gular plate. A single dorsal fin, nearly median, without adipose dorsal. Scales thin and cycloid, without bony layer. Lower Cretaceous to Kecent. Diplomystus, Cope. Abdomen compressed to a sharp edge, and bordered with large ridge scutes ; back between the occiput and dorsal fin armoured with smaller ridge scutes. D. dentatus, Cope, and other species finely preserved in the Eocene Green River Shales of Wyoming, U.S.A. Smaller species in the Upper Cretaceous of Mount Lebanon (D. brevissimus, Blv. sp.) and Brazil, and in the Oligocene of the Isle of Wight. Living in the rivers of New South Wales and Chili. Scombroclupea, but finlets spaced out between the small anal and the ^^^^j^^^^\3 Fig. 172. Clupea ventricosa, H. v. Meyer. Lower Miocene near Ulm, Wurteinberg. Unterkirchberg, Kner. As Clupea, forked caudal fin. S. macrophthahna, Heckel sp., from Upper Cretaceous of Mount Lebanon and Comen, Istria. Clupea, Linn. Herrings. (Fig. 172.) Abdomen compressed to a sharp edge, and bordered with large ridge scutes ; no dorsal scutes. jaws and palatines, larger on the vomer and hyoid. Meletta sardinites, Heckel. Fm. 173. Lower Oligocene Radoboj, Croatia (after Heckel). Teeth minute on the Dorsal fin small and sub-class vi TELEOSTEI 97 median. Xot certainly known below the Upper Eocene of Monte Bolca, near Verona. Small species in the freshwater Lower Miocene of Unterkirchberg, near Ulm, Wiirtemberg. Alosa, Engraulis, Cuv. Tertiary and Recent. Meletta, Val. (Fig. 173). Small slender fishes with thick cycloid scales, which are marked with three to six pairs of radiating grooves. Jaws tooth- less. Ventral ridge scutes large. Tertiary and Recent. Very common in the Lower Oligocene (Melettaschiefer) of the Carpathians, Croatia, Glarus, Alsace, etc. Family 7. Salmonidae. Salmon. As Clupeidae, but a small adipose fin behind the dorsal fin. Upper Tertiary and Recent. Fossil skeletons of the existing Mallotus villosus, Mull., are very common in nodules in Pleistocene Clay on the coast of Greenland and in the glacial deposits of Canada. Family 8. Osteoglossidae. Head bones much thickened, and cheek plates robust. Margin of upper jaw formed both by premaxilla and maxilla. Scales large and thick, composed of mosaic-like pieces. Upper Cretaceous to Recent. Phareodus, Leidy {Dapedoglossus, Cope). Laterally compressed deep- bodied fishes from the Eocene Green River Shales of Wyoming, U.S.A. (?) Brychaetus, Ag. London Clay ; Sheppey. Plethodus, Dixon. Cre- taceous ; England. Anogmius, Cope. Upper Cretaceous ; Kansas. Osteoglossum and other genera are large freshwater fishes living in the tropics. Family 9. Halosauridae. Gimther. Eel-shaped fishes with pectoral and pelvic fins, a short dorsal fin, an extended anal fin usually confluent with the diminutive caudal, and both head and trunk covered ivith cycloid scales. Margin of upper jaw formed both by premaxilla and maxilla. Verte- bral centra as delicate cylinders. Lateral line with luminous organs along the ventral border of the flank. Upper Cretaceous to Recent. Halosaurus, Johnson, living at great depths in the ocean. Echidnocephalus, W. von der Marck, an almost identical genus from the Upper Cretaceous of Sendenhorst, Westphalia. Family 10. Dercetidae. Smith Woodward (Hoplopleuridae, Pictet p.p.). Eel-shaped fishes with pectoral and pelvic fins, a more or less extended dorsal fin, and separate anal and caudal fins. Parietal bones large and in contact mesially ; premaxilla forming margin of upper jaw. Vertebral centra as delicate cylinders, with transverse processes bearing the ribs. No overlapping scales; but paired longitudinal series of bony scutes. Cretaceous. Dercetis, Agassiz. Snout elongated and pointed ; teeth minute and clustered. Dorsal fin occupying greater part of back, and pelvic fins inserted opposite to it ; anal fin short, opposite hinder end of dorsal ; caudal fin forked. Dermal scutes more or less angulated and ornamented with tubercles or spines ; VOL. II H 98 PISCES CLASS I two dorsal series, two ventral series, and a paired series supporting the lateral line. D. scutatus, Ag. Upper Cretaceous ; Westphalia. Leptotrachelus, W. v. d. Marck (Triaenaspis, Cope). As Dercetis, but dorsal fin not occupying more than middle third of back, and anal fin behind it. L. triqueter, Pict. sp., and other species from the Cretaceous of the Lebanon, Westphalia, and South Dakota, U.S.A. L. lewesiensis, Mant. sp., from English Chalk. Pelargorhynchus, v. d. Marck. Upper Cretaceous ; Westphalia. Stratodus, Cope. Premaxilla short, with several rows of teeth; palatine and mandibular teeth large, numerous, in several rows, all Avith pulp cavity. Upper Cretaceous ; Kansas. Family 11. Enchodontidae. Smith Woodward {Hoploplenridae, Pictet p.p.). Papacious fishes with more or less fusiform trunk. Parietal bones very small, separated by the supraoccipital ; delicate prem,axilla extended and nearly excluding the rod-like maxilla from the margin of the upper jaw, which bears very small teeth ; powerful teeth fused with the palato-pterygoid and dentary bones. Vertebral centra robust, none with transverse processes. A small adipose fin probably present behind the single dorsal fin. No scales ; but a median seizes of dorsal bony scutes, and often a paired series of similar scutes supporting the lateral line. Cretaceous. Enchodus, x\g. (Eurygnathus, Davis ; Ischyrocephalus, v. d. Marck ; Holcodon, Kramb.), (Fig. 174). The largest and longest tooth at the anterior end of the palatine ; large teeth of dentary spaced, increas- ing in length to the sym- physis. External bones more or less tuberculated. Three or four oval median scutes between the occiput and dorsal fin ; an adipose dorsal on the tail ; caudal fin forked. No postclavi- cular plate ; no scutes along course of lateral line, but a recurved hooklet on each side of the caudal pedicle. E. lewesiensis, Mant. sp., from the Lower Chalk, S.-E. England. Well-preserved skeletons of other species in the Upper Cretaceous of West- phalia and the Lebanon. Fragments in the Upper Cretaceous of North America, and Maastricht Beds, Holland. Eurypholis, Pictet (Saurorhamphus, Heckel). As Enchodus, but a large postclavicular plate, and well-developed scutes along the course of the lateral line. E. boissieri, Pictet, from Upper Cretaceous of Hakel, Mount Lebanon. An imperfectly known species, erroneously restored by Heckel under the name of Saurorhamphus freyeri, Heck., from Lower Cretaceous, Comen, Istria. Cimolichthys, Leidy. Largest teeth in middle of palato-pterygoid arcade semi-barbed at apex. Clustered teeth in mandible, with simply pointed larger teeth at intervals. C. lewesiensis, Leidy, from Lower Chalk, S.-E. England. The semi-barbed teeth common in the European Chalk, known also in North America. Prionolepis, Egert. ; Leptecodon, Williston. Upper Cretaceous. 174. Imperfect dentary bone of Enchodiis lewesiensis, Mant. sp, Lower Chalk ; Lewes (after Agassiz). SUB-CLASS VI TELEOSTEI 99 Halec, Ag. (PomognatKus, Dixon; Archaeogadus, v. d. Marck). Premaxilla very slender, with minute teeth ; maxilla equally slender, with a few relatively large spaced teeth at its hinder end. Palato-pterygoid teeth closely arranged, laterally compressed cones, largest in the middle of the arcade. No dermal scutes, except a pair of recurved hooklets on the caudal pedicle. H eupterygius, Dixon, well preserved in Lower Chalk, S.-E. England. Halec sternbergi, Ag., in Turonian, Bohemia. Other species in Upper Cretaceous, Mount Lebanon, and in Lower Cretaceous, Isle of Lesina, Dalmatia. Empo, Cope. Double series of teeth on palatine, none barbed. Premaxilla elongate, with one row of small teeth ; mandibular teeth in two series, of which the outer are small and in several rows, while the inner are very large. Upper Cretaceous of Kansas and S.-E. England. Family 12. Scopelidae. Premaxilla much extended, excluding maxilla from upper margin, of mouth. Skull and skeleton as in Enchodontidae. A small adipose fin behind the dorsal Jin. No air bladder. Trunk naked or scaly, without bony scutes. Cretaceous to Recent. Exclusively marine fishes, for the most part pelagic or deep-sea forms. SardinioideSj v. d. Marck. Teeth minute ; maxilla expanded behind. Dorsal fin median ; paired fins small ; caudal fin slightly forked. Scales large, serrated at the hinder border. S. monasters, Ag. sp., from Upper Cretaceous, Sendenhorst, Westphalia. Other species from Mount Lebanon. Sardinius, v. d. Marck. Upper Cretaceous ; Westphalia. Leptosomus, v. d. Marck. Upper Cretaceous ; Westphalia and Mount Lebanon. Opisthopteryx, Pictet and Humb. Lebanon. Scopeloides, Wettstein. Upper Eocene ; Canton Glarus. Parascopelus, Anapterus, Sauvage. Upper Miocene ; Licata, Sicily. Bhinellus, Ag. (Ichthyotringa, Cope), (Fig. 175). Slender fishes with very large pectoral fins, and the premaxillae produced forwards into a long pointed Fig. I7"j. Jlhinelltis furcatus, Ag. Upper Cretaceous ; Sendenhorst, Westphalia (after W. v. Marck). rostrum. Teeth slender and pointed. Dorsal fin small, in advance of the still smaller anal fin ; caudal fin forked. Scales smooth, slightly enlarged along the course of the lateral line. Upper Cretaceous; Westphalia, Mount Lebanon, and Dakota. 100 PISCES class i Family 13. G-onorhynchidae. Premaxilla smaller than maxilla, but excluding latter from margin of upper jaw. No adipose dorsal Jin. No air bladder. Scales deeply overlapping, fringed behind with short spines. Cretaceous to Recent. Charitosomus, W. v. d. Marck. Upper Cretaceous ; Westphalia and Lebanon. Notogoneus, Cope (Sphenolepis, Ag.). Freshwater Eocene (Green River Shales) ; Wyoming, U.S.A. Upper Eocene ; France and Germany. Family 14. Cheirothricidae. Smith Woodward. Scopeloids with enormously enlarged pelvic fins. Abdominal vertebrae with trans- verse processes. Cretaceous. Cheirothrix, Pictet and Humbert (Megapus, Schliiter ; Megistopus, Landois). Branchiostegal rays very large, eight or nine in number. Pectoral fins compara- tively small and delicate, with only one ray considerably elongated ; the enlarged pelvic fins close to the pectorals, with about seventeen rays ; dorsal fin deep, arising immediately behind the head ; anal fin small ; caudal fin forked. C. libanicus, P. and H., from Upper Cretaceous, Mount Lebanon. C. guestphalicus, Schliiter sp., from Westphalia. Family 15. Esocidae. Pikes. Trunk elongated, with large cycloid scales. Premaxilla and maxilla entering upper border of mouth. Premaxilla, mandible, palatine, and vomer with stout, pointed teeth ; maxilla toothless. Dorsal fin remote. Miocene to Recent. Fine specimens referable to the existing genus Esox, Cuv., occur at Oeningen and in other Miocene freshwater formations in Europe. Family 16. Cyprinodontidae. Toothed carps. Small freshwater fishes with cycloid scales. Premaxilla excluding maxilla from upper margin of month ; no barbels. Margin of jaws and pharyngeal bones with pointed teeth. No anterior vertebrae fused together. No adipose dorsal fin. Tertiary and Recent. Of the genera of this family, Prolebias, Sauvage, Uto. vuyeri, Ag." ^torinella-clay ; allied t0 LMaS ^ CuV ' ( Fi g' 176 > is remarkably COUl- Fran'kfurt-a.-M. Nat. size. m0 n in the Oligocene and Miocene of Europe. Family 17. Oyprinidae. Carps. Freshwater fishes with cycloid scales. Premaxilla excluding maxilla from upper margin of mouth ; barbels present or absent. Mouth toothless, but lower pharyngeals falciform and bearing one to three rows of hollow prehensile teeth. Usually only three branchiostegal rays. Anterior vertebrae fused together, and air bladder connected with organ of hearing by a chain of ossicles. Upper Tertiary and Recent. The Cyprinoids are numerous in the fresh-waters of the Old World and SUB-CLASS VI TELEOSTEI North America, but do not occur in South America, fossil species, all from fresh- water formations, belong to the existing genera Leuciscus, Klein (Fig. 177), Tinea, Gobio, Barbus, Cuv., Bhodeus, Aspius, Ag. (Fig. 178), Cyprinus, Cobitis (Artedi), Linn., Nemachilus, Cuv., Thynnichthys, Bleeker, etc. The only extinct genera, such as Amyzon, Diastichus, Oligobelus, Cope, and others, are closely related to existing forms. 101 Most of the known Fig. 177. Scales of Leuciscus oeningensis, Ag. Upper Miocene ; Oeningen, Baden. Enlarged (after Winkler). Fig. 17S. Pharyngeal bones and teeth of Aspius rapax, Ag. Recent (after Heckel and Kner). Siluridae. Cat-fishes. Family 18. Scaleless fishes, naked or armoured with bony plates. PremaxiUa excluding maxilla from upper margin of mouth, the rudimentary maxilla usually supporting a barbel. Snboperculum absent. Infraclavicular plates present. Anterior pectoral fin ray usually a strong bony spine. Anterior vertebrae and air bladder as in Cyprinidae. Eocene to Recent. The Siluroids form a very numerous family of freshwater fishes, ranging over all temperate and tropical regions, and a few sometimes passing into the sea round the coasts. Fossil remains are rare, and represent fishes closely resembling those still surviving. The oldest known fragment is a portion of head (Bucklandium diluvii, Konig) from the London Clay of Sheppey. Typical remains of Arius occur in the Middle and Upper Eocene of the Hampshire Basin and Belgium. Other genera are recorded from the Eocene of Wyoming, U.S.A. (Bhineastes, Cope), the Lower Pliocene of the Siwalik Hills, India, and a Tertiary Lignite near Padang, Sumatra. Family 19. Muraenidae. Eels. Body much elongated, cylindrical or ribbon-shaped. Premaxillae fused with ethmoid and vomer ; upper jaw formed laterally by the toothed maxilla. Dorsal fin much extended, often meeting the anal round the tail. Pectoral arch not suspended from the cranium ; pelvic fins wanting. Skin naked, or with small, rudimentary, cycloid scales. Upper Cretaceous to Recent. Urenchelys, Sm. Woodw. With separate caudal fin. Upper Cretaceous ; Sahel Alma, Lebanon, and English Chalk. Eomyrus, Storms. Middle Eocene ; Belgium. Species of existing genera from marine Upper Eocene, Monte Bolca, and freshwater Upper Miocene, Oeningen. Order 2. PHYSOCLYSTI. Gill. Air bladder, when present, not connected by a tufje with the oesophagus in the adult (except in certain Berycidae). Gills pectinate. Pelvic fins usually far forwards ; fin rays articulated or spinous. Scales, when present, cycloid or ctenoid. 102 PISCES CLASS I Sub-Order 1. ANACANTHINI. Miiller. All fin rays flexible and articulated. Pelvic fins jugular or thoracic. Pharyngeal bones not fused together. Family 1. Gadidae. Cod-fishes. Elongated fishes with broad head, and the toothed premaxilla excluding the maxilla from the upper margin of the mouth. t Pelvic fins jugular. Dorsal fin extending almost the whole length of the back, sometimes subdivided into two or three parts ; anal fin much extended, sometimes divided into two. Scales small and smooth. Eocene to Recent. Fossil representatives of this family are rare. Nemopteryx troscheli, vom Rath, occurs in the Upper Eocene slates of Canton Glarus. Remains of Phycis, Strinsia, Gadus, and Brosmius have been described from the Miocene of Hungary, Croatia, and Sicily. Undetermined skulls are known from the London Clay of Sheppey. Family 2. Pleuronectidae. Flat-fishes. Disc-shaped fishes, much laterally compressed and asymmetrical, with both the eyes on one side of the head — the upper side when at rest. Dorsal and anal fins extending almost the whole length of the trunk. Pelvic fins jugular, in front of the pectorals. Air bladder absent. Scales, when present, minute and ctenoid; upper side of body coloured, lower side colourless. Upper Eocene to Recent. The flat-fishes are very numerous in the existing fauna, living on sandy coasts, and some of them entering the mouths of rivers. They are extremely Fig. 179. Solea kircTibergana, H. v. Meyer. Lower Miocene ; Unterkirchberg, near Ulm. Nat. size, rare among fossils. A small species of Rhombus, Klein, occurs in the Upper Eocene of Monte Bolca. Solea, Cuv., is known from the Lower Miocene of AViirtemberg (Fig. 179). Sub-Order 2. PHARYNGOGNATHL Miiller. Fin rays articulated or partly spinous. Lower pharyngeal bones fused together, SUB-CLASS VI TELEOSTEI 103 Family 1. Scombresocidae. Premaxilla and maxilla forming margin of upper jaw. Pectoral fins sometimes much enlarged, wing-like ; pelvic fins abdominal ; dorsal fin remote, opposite the anal fin; all fin, rays articulated and flexible. Scales cycloid. Eocene to Recent. Holosteus, Ag., from the Upper Eocene of Monte Bolca, and extinct species of Belone, Cuv., and Scombresox, Lacep., from the Miocene of Europe, are referred to this family. Family 2. Pomacentridae. Short, laterally compressed, spiny -finned fishes, with ctenoid scales. Dentition feeble. Palatines toothless. Pelvic fins thoracic, with one spine and five divided rays ; dorsal fin extended, with numerous spines ; anal fin with two or three spines. Eocene to Recent. Here are placed Odonteus, Ag., from the Upper Eocene of Monte Bolca, and Priscacara, Cope, from the Eocene Green River Shales of Wyoming. Family 3. Labridae. Wrasses. Brilliantly coloured fishes with cycloid scales and thick fleshy lips. Teeth on margin of jaws powerful; palate toothless. United lower pharyngeals much thickened and forming a plate beset with rounded, rarely acuminate grinding teeth; upper pharyngeals usually separate, bearing similar teeth. Eocene to Recent. The wrasses chiefly inhabit tropical seas at the present day. Phyllodus, Ag. (Fig. 180). Known only by pharyngeals bearing smooth, thin, flattened grinding teeth. Grinding surface of upper plate slightly concave, lower convex. Teeth arranged in rows, the middle row large. Several layers of successional teeth usually lie beneath those in function. Eocene and Miocene ; Europe and North America. Nummojpalatus, Rouault (Pharyngodopilus, Cocchi), (Fig. 181). Lower pharyngeals triangular, covered with a pavement of numerous, small, round or oblong grinding teeth, of which there are always several superimposed layers. Upper pharyn- geals separate, triangular, covered with grinding teeth. Eocene ; Virginia. Miocene and Pliocene ; Europe. Taurinichthys, Cocchi. Miocene. f ig . !8i. The existing genera Labrus, Artedi, Nummopalatus multidens, Miinst. sp. Miocene; Neu- and ScciVUS, Forsk., are also represented dorfl a. d. March. A, Lower pharyngeal with dentition. • ,v jt ^ T^«j-, - ~„,"^ B, An npper pharyngeal. Nat. size. in the Upper lertiaries. Fig. ISO. Phyllodus medius, Ag. Lower pharyngeal denti- tion, nat. size. Lund' in Clay ; Sheppey (aftei Cocchi). 104 PISCES CLASS I Sub-Order 3. ACANTHOPTEM. Muller. Some of the rays of the pelvic and median fins spinous, not articulated. Pelvic fins usually advanced far forwards. Lower pharyngeals separate. In the existing fauna the Acanthopteri form by far the most numerous group of fishes. Family 1. Berycidae. Trunk short, compressed, and rather deep, with ctenoid or cycloid scales, rarely naked. Head bones ridged to form large mucous-cavities ; orbits large and lateral ; mouth usually oblique, the jaws and generally also the palate with small pointed teeth. Operculum more or less serrated or ridged. Pelvic fins thoracic, with an anterior spine and more than five divided rays. Upper Cretaceous to Recent. The living Berycidae are marine fishes, most of them inhabitating consider- able depths. Hoplopteryx, Ag. (Fig. 182). Head short. Dorsal fin deep, with a few spaced spines in front ; anal fin with four or five spines. Scales large and Fig. 182. Hoplopterys zippei, Agassi* sp. Lower Planer ; Wehlowitz, Bohemia. 1/3 nat. size (after Fritsch). ctenoid. Common in the Upper Cretaceous. H. lewesiensis, Mant., from the English Chalk, and other species originally referred to the surviving genus Beryx. Sphenocephaly, Ag. Upper Cretaceous, Westphalia. Pycnosterinx, Heckel. Upper Cretaceous, Mount Lebanon. The two surviving genera, Holocentrum and Myripristis, Cuv., are repre- sented by extinct species in the Upper Eocene of Monte Bolca. Family 2. Percidae. Perches. Trunk elongated, with ctenoid scales. Premaxilta, mandible, vomer, and palatine with pointed teeth ; six or seven branchiostegal rays. Pelvic fins thoracic with an SUB-CLASS VI TELEOSTEI 105 anterior spine and not more than five divided rays ; one or two dorsal fins, the fore- most part with long spines. Eocene to Recent. The perches are predaceous fishes of the tropical and temperate seas and fresh-waters. Numerous fossil representatives occur in the Tertiary formations of Europe and North America. Some belong to extinct genera, such as Paraperea, Sauvage, Smerdis, Ag. (Fig. 183), Acanus, Ag., Mioplosus, Cope, and Erisma- topterus, Cope. Others have been referred to the existing genera Serranus, Pelates, Dules, Gerres, Labrax, and Lates, Cuv. i-'lG. 183. Smerdis mimitus, Ag. Oligocene ; Aix, Provence. Nat. size. Family 3. Sparidae. Sea-breams. Brightly coloured, rather deep-bodied fishes, with very delicately serrated ctenoid scales. Margin of jaws provided in front with conical or cutting teeth of different shapes, which are usually followed behind by several rows of round or oval grinding teeth ; palatine and vomer toothless. Pelvic fins thoracic, with one spine and five divided rays; dorsal fin single, the anterior spinous part almost similar to the posterior soft part ; anal fin with three spines. Cretaceous to Recent. The sea-breams, which are easily recognised by their peculiar dentition, live at the present day in the tropical seas, feeding especially on Mollusca and Crustacea, which they crush with their teeth. Spar nodus, Ag., occurs in the Upper Eocene of Monte Bolca. Sargus, Cuv., Trigonodon, Sismonda (Fig. 184), and Fig. 184. Premaxillae of Sargus, outer (A) and inner (JS) views. Recent ; Mediterranean. Nat. size. Fig. ISO. Right premaxilla of Chrysophrys aurata, Linn. Inner aspect. Recent ; Mediter- ranean. Nat. size. Chrysophrys, Cuv. (Capitodus, Miinst.), (Fig. 185), range from the Miocene to existing seas. Stephanodus, Zittel. Cutting teeth from Upper Cretaceous, Libyan Desert. The families Pristipomatidae, Scorpaenidae, Teuthididae, Xiphiidae, and Chaetodontidae are represented in the Tertiaries by fishes scarcely differing from the surviving forms. Family 9. Palaeorhynchidae. Elongated,, low, and laterally compressed fishes. Snout produced into a long beak; jaws toothless or with very small denticles. Vertebrae long and slender; 106 PISCES CLASS I spinous processes and ribs delicate. Pelvic fins thoracic, with several rays; dorsal fin extending from the occiput to the tail ; anal fin extending from the anus to the cleft caudal fin. Eocene. The two sufficiently well-known genera Palaeorhynchus, Blv., and Hemi- rhynchus, Ag., occur abundantly in the Middle Eocene Calcaire Grossier of Fig. 186. Palaeorhynchus zitteli, Kramb. sp. Upper Eocene ; Rajcza, Galicia. i/giiat. size. Paris, the Upper Eocene sandstone of Galicia, in the black slates of Glarus, and near Buchsweiler in Alsace. P. glarisianus, Blv., H. deshayesi, Ag., and P. zitteli, Kramb. sp. (Fig. 186). Family 10. Trichiuridae. Elongated and laterally compressed, almost ribbon -shaped predaceous fishes. Fig. 1S7. Lepidopus (Anenchelum) glarisianus, Ag. Upper Eocene ; Matt, near Glarus. A, Head. B, Portion of trunk. Nat. size (after Wettstein). Gape of mouth wide, jaws and palatine bones with powerful conical teeth. Dorsal SUB-CLASS VI TELE0STE1 10' and anal fins much extended with unarticulated spines; pelvic fins sometimes rudi- mentary or wanting. Upper Eocene to Recent. The Trichiuridae are predaceous fishes of the tropical and sub-tropical seas, living both near the coasts and also in deep water. Several well-marked fossil forms occur in the Eocene and Miocene. Extinct species of the existing Lepidopus, Gouan (Anenchelum, Blv., Lepido- pides, Heckel), are found in the black slates of G-larus (Fig. 187), in the Menilite shales of the Carpathians (L. carpathicus, Kramb.), and in the Upper Miocene of Sicily and Tuscany. Trichiurichthys, Hemithyrsites, Sauvage. Upper Miocene ; Licata, Sicily. Family 11. Acronuridae. Trunk deep and laterally compressed, covered with small scales. The tail in adult examples provided with one or several bony plates or spines. . Jaws with a row of cutting teeth. Anal fin with three spines. Eocene to Recent. The living genera dwell chiefly in the vicinity of coral reefs. The existing genera Acanthurus, Forsk., and Naseus, Commerson, are recorded from the Upper Eocene of Monte Bolca ; the former also from the Calcaire Grossier of Paris and the Miocene of Vienna. Aulorhamphus, Zigno (Calamostoma, Steind. non Ag.). Eocene. Family 12. Carangiclae. Horse-mackerels. Trunk laterally compressed, deep or elongated, naked or with small scales. Teeth conical. Spinous portion of the dorsal fin shorter than the soft portion : pelvic fins thoracic, sometimes rudimentary or absent. Eocene to Recent. Marine predaceous fishes of the tropical and temperate zones, common in Tertiary formations. PI at ax, Cuv. Fossil in the Upper Eocene of Monte Bolca and in the Crag (Lower Plio- cene) of Norfolk Recent. Z a nclu s, Com m e r s. Eocene and Recent. Semiophorus, Ag. (Fig. 188). Other genera with extinct representatives are the following : — Amphistium, Fig. 1SS. Semiophorus velifer, Ag. Upper Eocene ; Monte Bolca. 1/2 nat. size (after Agassiz). Upper Eocene ; Monte Bolca and Belgium. 108 PISCES class i Ag., Vomer, Cuv., Caranx, Cuv., Carangopsis, Ag., Lichia, Cuv., Ductor, Ag., Trachinotus, Lacep., Seriola, Equnla, Cuv., Acanthonemus, Ag., etc. Family 13. Coryphaenidae. Trunk laterally compressed. Teeth small and conical or wanting. Dorsal Jin extended, without spines. Eocene to Recent. Here is placed the genus Mene, Lacep. (Gasteronemus, Ag.), with extinct species in the Upper Eocene of Monte Bolca. Family 14. Scombridae. Mackerels. Trunk elongated, naked or with small scales. Teeth conical. Pelvic fins thoracic ; two dorsal fins, the hinder usually consisting of separate tufts. Eocene to Recent. Thynnus, Cuv. The existing tunny. Mostly large cylindrical fishes, covered with small scales. Anterior dorsal fin with twelve to fourteen spines, which are not remarkably elongated ; six to nine small, separate, tufted fins behind the posterior dorsal fin. Teeth small. Several species in the Upper Eocene of Monte Bolca, the Miocene of Oran, Algeria, and the Pliocene Crags of Belgium and England. The genera Palimphyes, Ag. ; Isurichthys, Woodw. ; Opisthomyzon, Cope (allied to Echeneis, Art.), occur in the black slates of G-larus ; Orcynus, Cuv., in the Upper Eocene of Monte Bolca ; Megalolepis, Kramb., in the Lower Menilite shales of Baschka in Galicia. The existing genera Scomber, Art., Auxis, Cuv., are represented in the Miocene of Croatia, and Cybium, Cuv., in the Eocene, Oligocene, and Miocene. The families Cyttidae, Trachinidae, Lophiidae, Cataphracti, Cottidae, Bleniidae, and Gobiidae have very few fossil representatives in the Tertiary. The earliest members of the families Mugilidae, Sphyraenidae, and Atherinidae occur in the Upper Cretaceous of England, Colorado, and New Mexico (Calamopleurus, Dixon ; Syllaemus, Apsopelix, Pelycorapis, Cope). Sphyraena, Bloch, Bhamphognathus, Ag., Mesogaster, Ag., and Atherina, Linn., occur in the Upper Eocene of Monte Bolca ; Mugil princeps, Ag., in the Upper Eocene of Aix-en-Provence. Family 25. Aulostomidae. Flute-mouths. Elongated marine fishes, with elongated tube-shaped snout and remote dorsal fin. Occiput movably articulated with the vertebral column; teeth small. Spines little developed. Pelvic fins abdominal or thoracic. Scales small or absent. Eocene to Recent. At the present day the Aulostomes fig. is9. . chiefly inhabit tropical seas. Fistu- Amphisyle heinrichsi, Heckel. Upper Eocene; laria , LillTl., and Auhstoma, Lac6p., and Krakowiza. Carpathians. Nat. size (after Heckel). , 7-7-7*1 the extinct genera Urosphen, Ag., and Bhamphosus, Ag., occur in the Upper Eocene of Monte Bolca. The small, dorsally armoured genus Amphisyle, Klein, which still survives, characterises SUB-CLASS VI TELEOSTEI 109 the Upper Eocene Menilite shales of Galicia (Fig. 189), and the Meletta shales in Upper Alsace and the Vienna Basin. Family 26. Blochiidae. Elongated fishes with very long beak- shaped snout, which is formed by the equal/// produced and finely toothed jaws. The entire trunk covered with cordiform or rhombic bony scales, which are mostly keeled and overlap each other. Pelvic fins small, beneath the pectoral pair ; dorsal fin arising at the occiput and extending Fig. 190. JJlochius longirostris, Volta. Upper Eocene ; Monte Bolca. Ve na t- size (after Agassiz). almost to the caudal fin, composed of a spaced series of long spines; anal fin also much extended ami consisting of similar spines ; caudal fin large. Eocene. The only known genus is Blochius, Volta (Fig. 190), from the Upper Eocene of Monte Bolca. Sub-Order 4. LOPHOBRANCHII. Cuvier. Gills arranged in tufts on the branchial arches and protected by an operculum. Snout with tubular extension, and jaws toothless. Pelvic fins, often also the anal and caudal fins wanting. Skin armoured with thin bony plates. Only very few fossil representatives of the two families of this remarkable group are known. The elongated Solenostomidae, in which all the fins are developed, have an Eocene forerunner in the genus Solenorhynchus, Heckel, from Monte Postale. Extinct species of Siphonostoma, which is still common / j 1 i 'r'f'r ^; f i^iT'r/"" ^r 1 ' P^^rTTrTil^-n.liiJ:;^:!;::;:!::::^,::;,!^;^;^. Fig. 191. Siphonostoma albyi, Sauvage. Upper Miocene ; Licata, Sicily (after Sauvage). in the Mediterranean, also occur in the Upper Miocene of Licata, Sicily (Fig. 191), and of Tuscany. Several Tertiary forms of Syngnathidae are known ; Syngnathus, Pseudosyngnathus, and an extinct genus Calamostoma, Ag., occur in the Eocene. Sub-Order 5. PLECTOGNATHI. Cuvier. Skin covered with roughened scales, bony spines or plates, rarely naked. Skeleton incompletely ossified. Maxillae and premaxillae fused together into a solid beak. Gills pectinate. Pelvic fins wanting or represented by spines ; dorsal fin with articulated rays opposed to the anal fin. Fig. 192. 110 PISCES class i Family 1. Gymnodontidae. Olivier. Trunk short and deep, naked or covered with bony spines. Jaws beak-shaped, with a cutting dental plate above and below, either undivided or in right and left halves. No dorsal spines. Eocene to Recent. Fossil remains of this family are very rare. Large jaws of Orthagoriscus have been found in the Oligocene of Belgium. Dioclon occurs in the Eocene, Oligocene, and Miocene ; Gymuodus in the Miocene ; Heptadiodon in the Upper Eocene of Monte Postale. Family 2. Sclerodermidae. Cuvier. Jaws with a small number of separate teeth. Skin with scales or roughened. Dorsal spines usually present. Eocene Pharyngeal teeth. A, An- to Recent. eistrodon libycus, Zitt. Upper „. .. „ i -n ?• . /t» » Chalk; Gasr Dachi, Libyan 1 he existing genera Ustracion and Batistes (rroto- (?,mr5S;Ge 7 rVafs^p. iS Eocene'; oalistum, Massal.) have representatives in the Upper Mukattam, near Cairo (after Eocene of Monte Bolca. The extinct genera Acantho- Daines). 1/77 derma and Acanthopleurus, Ag., occur in the Upper Eocene black slates of G-larus. The teeth described as Ancistrodon, Roemer (Fig. 192), from the Upper Cretaceous, Eocene, and Oligocene, may belong, at least in part, to the pharyngeal dentition of Scleroderms. Range and Distribution of Fossil Fishes. Notwithstanding the apparently favourable circumstances for the preserva- tion of fishes due to their aqueous habitat, their geological history is still very imperfectly known. Complete skeletons, it is true, are rather numerous in clayey, calcareous, or marly shales, which were laid down as fine mud on the bottom of former lakes and near the shore in seas. On the other hand, in rocks of coarser grain (sandstone), in very many shore deposits, and also in deep-sea limestones, there are usually only isolated teeth, scales, dermal plates, vertebrae, scattered bones of the skeleton, and otolites, which are extremely difficult to determine. In very many marine, lacustrine, and fluviatile deposits, fish remains are almost completely wanting, so that the formations rich in fossils are usually separated from each other by a series of strata which represent long periods of time. The oldest undoubted traces of fishes both in Europe and North America occur in rocks of Silurian age. They are found in the Ludlow Bone-bed, in the light, dolomitic, fissile limestone of the island of Oesel in the Baltic, and in sandy shales in Podolia and Galicia. They are also found in the Onondaga Group of Pennsylvania. The determinable forms are all Selachii and primi- tive Ostracodermi (Coelolepidae, Pteraspidae, and Cephalaspidae). In the Devonian era fishes begin to attain a great development, and are sometimes discovered in a remarkable state of preservation, especially in the Old Red Sandstone of Great Britain, the Russian Baltic provinces, Podolia, and Galicia, and in the corresponding formations of North America. Scattered fish remains, such as plates of Ostracodermi and spines of Selachii, also occur in the uppermost stages (F, G) of the Silurian basin of Bohemia, and in the phylum viii VERTEBRATA 1 1 1 Devonian of the Eifel, Nassau, Westphalia, and Belgium. .Gigantic Arthrodires (DinicMhys, Titanichthys, Diplognathus) and Selachii are remarkably abundant in the Middle and Upper Devonian of Ohio, Wisconsin, and New Vork. The Devonian fish fauna consists of Arthrodires, Ostracoderms, many Ganoids (Crossopterygii and Heterocerci), Dipnoans (Ctenodipterini), and Selachians (Pleuropterygii, Acanthodii, Holocephali). The fishes of the Carboniferous System are obtained partly from the marine Carboniferous Limestone, partly from the shales and sandstones of the productive Coal Measures. The enormous development of the Selachii, 1 of which, however, only teeth and fin spines are commonly preserved, sharply distinguishes the Carboniferous fish fauna from that of the Devonian period. The Cochliodontidae, Psammodontidae, and Petalodontidae are almost ex- clusively confined to the Carboniferous Limestone, while the Cestraciontidae are also well represented ; the Acanthodians and Pleuropterygians continue, the Pleuracanthidae begin. The heterocercal Ganoids are the principal associates of the Selachii ; the Crossopterygii and Ctenodipterini are still present, but in diminished numbers. The fishes of the Permian system are closely similar to those of the pro- ductive Coal Measures. They occur in the Rothliegenden of the Saar Basin, Bohemia, Saxony, Silesia, and France ; in the Magnesian Limestone of England ; in the Kupferschiefer of Thuringia and Hesse ; and in the probably contempor- aneous strata of Texas and New Mexico. The Heterocerci are by far the most numerous. Of the Crossopterygii, Coelacanthus and Megalichthys alone survive in Europe. Among the Dipnoi, the genera Ctenodus and Sagenodus are especially widely distributed. In comparison with the Carboniferous fish fauna, that of the Permian period is noticeably destitute of Selachii. Here, however, the remarkable Pleuracanthidae attain their maximum development, and are associated with a few Cochliodontidae (Menaspis), Petalodontidae (Janassa), and Acanthodidae. The abrupt break in development, which is observable in most sections of the animal and plant world at the close of the Palaeozoic epoch, is also conspicuous among the fishes, although the Triassic fish fauna exhibits many resemblances to that of the Permian. Among Selachii, the Pleuracanthidae, Cochliodontidae, and Petalodontidae are wanting ; the Plagiostomi, on the other hand, are well represented. Teeth and fin spines of the Cestraciontidae, for example, are very numerous in the Muschelkalk and uppermost Keuper. The occurrence of heterocercal scaly Ganoids of the family Palaeoniscidae, as well as the persistence of a few Crossopterygians, is indeed reminiscent of Palaeozoic times ; but the most numerous and best preserved Triassic fishes belong to the enamel-scaled Lepidostei, of which the Permian system affords only a single genus (Acentrophorus). Among the Dipnoi the persistent Ceratodus, represented principally by teeth, plays an important part. The Teleostei are already represented by some small Clnpeoids (Megalopterus). The fish fauna of the Lias is a direct continuation and further development of that of the Trias. Xo less than 152 species were described by Agassiz and Egerton, and of these 79 occur only in the Lower Lias of Lyme Regis in Dorset. The Middle Lias contains few fishes ; but the Posidonia shales and bituminous limestone of the Upper Lias e in Swabia and Franconia, as well as 1 Hay, 0. P., The Chronological Distribution of the Elasmobranchs (Trans. Amer. Phil. Soc. vol. XX.), 1901. 112 PISCES class i the corresponding strata of Werther, near Halle, the Departments of Calvados, Yonne, and Cote-d'Or in France, and of Ilminster and Whitby in England, again yield a considerable number of species. The Selachians persist in undiminished numbers. Undina gulo, Egerton, from Lyme Regis represents the Coelacanthidae, Chondrosteus the cartilaginous ganoids. The majority of the Liassic fishes, however, belong to the scaly Ganoids of the order Lepidostei, though a few genera of the heterocercal Palaeoniscidae still survive. A new element in the Liassic fish fauna is formed by the thin-scaled Amioids, in which the vertebral column is still bent upwards to the upper lobe of the tail, and remains incompletely ossified. A single species from the Lower Lias of England (Mesodon liassicus, Eg.) indicates the first appearance of the Pycnodontidae. Among bony fishes a few small Clupeoids (Leptolepis) may be mentioned. Ceratodus and Pholidophorus are present in the Lower Jura of the Western United States. In the Middle Jura shaly deposits with well-preserved fish skeletons are wanting. Our knowledge of the fish fauna of the period is thus confined to detached teeth, fin spines, bones, and scales, which occur occasionally. Almost all the genera observed in the Dogger occur in addition in the Lias or the Upper Jurassic. Of the latter the most numerous discoveries have been made in the fissile limestones of the neighbourhood of Solenhofen, Kelheim, and Eichstaclt in Bavaria, Nusplingen in Wiirtemberg, and Cerin in the Department of Ain, France. An abundance of beautifully preserved skeletons of Selachians, Ganoids, and Teleosteans have been obtained from these localities, to which must be added the Portlandian Limestone of Soleure, Neuchatel, Hanover, and Boulogne-sur-Mer, and the Purbeck Beds of England as formations yielding well-preserved jaw-bones, teeth, spines, scales, and vertebrae. The heterocercal Palaeoniscids have become reduced to a single genus (Coccolepis). Of sharks and rays, complete or partially well-preserved skeletons are known, which indicate close relationships or absolute identity with various still surviving genera. The Cestraciontidae and Lamnidae are also represented by several extinct genera, and the Holocephali are much more numerous than in the Lias. Among the Ganoids the Coelacanthidae attain their maximum development in varied forms. The large majority of the Upper Jurassic fishes consist of Lepidostei and Amioidei, with Teleostei of the family Leptolepidae. With the beginning of the Cretaceous system there is an important change in the fish fauna, so that the previously dominant Ganoids become more and more displaced by Teleosteans. This substitution is almost complete in the middle and upper divisions of the Chalk ; in the Lower Cretaceous, on the other hand, there are still a few types of Ganoids surviving from Jurassic times. The fish fauna of the Cretaceous system thus falls into two well- marked sections, to the lower of which belong the light-coloured fissile lime- , stones of Pietraroza, the limestones of Castellamare, and Torre d'Orlando near Naples, of Comen (Istria), Crespano (Vicentin), Lesina (Dalmatia), and Grodischt in the Carpathians, and the Neocomian deposits of the Voirons, near Geneva. The normal deposits of the Middle and Upper Chalk chiefly contain teeth, vertebrae, and isolated fragments of Selachians, Chimaeroids, Pycnodonts, and Physostomes ; the fissile limestones of the Lebanon, the marly sandstone of Westphalia, and the Niobrara Chalk of Kansas, on the other hand, yield a con- siderable number of well-preserved skeletons. Among these the Ganoids are phylum vin VERTEBRATA 113 extremely rare, while the Physostomi constitute about three-quarters of all the known species. The Physoclysti, like the Physostomi, are represented chiefly by extinct genera. With the beginning of the Tertiary period there is a still closer approxima- tion to the condition of affairs at present prevailing. The oldest Eocene fish fauna of Europe, from the London Clay of southern England, is incompletely investigated. The contemporaneous deposits in the Paris Basin yield only a few fish remains, but among these are scales of the Ganoid genus LepiJosfeus, which still exists in North America. The most important and best known deposit of Eocene fishes is the light-coloured fissile limestone of Monte Bolca, near Verona, which corresponds in age approxi- mately with the Calcaire Grossier of the Paris Basin. No less than 94 genera and 170 species, including several sharks and rays, have been described from it. Of Ganoids only the Pycnodonts here survive ; all the other fishes belong to the Teleostei, most of them indeed to genera which at present live in the Indo-Pacific and Eed Sea, in the tropical Atlantic, and to a smaller degree also in the Mediterranean. The most interesting feature in this fauna is the great increase of the Acanthopteri and the decrease of the Physostomi. A remarkable fish horizon, partly marked by deep-sea fishes, occurs at the summit of the Eocene, represented in the black slates of Matt in Canton Glarus, the contemporary Menilite Shales of Styria, Upper Bavaria (Siegsdorf), Upper Alsace, and other localities. From Glarus, the richest locality for this zone, 29 species of fishes are known, according to Wettstein, and all of these belong to the Teleostei. In a remarkable way the extinct genera here considerably exceed those which survive to the present day. In the western states of North America, in the so-called Puerco, Wasatch, and Bridger formations of New Mexico and "Wyoming, fossil fishes are also abundant ; but these, since they occur in freshwater deposits, have little in common with the Eocene forms of Europe, which are met with almost exclusively in marine or estuarine deposits. It is interesting to note that the existing North American Ganoid families, Lepidosteidae and Amiidae, are represented here. The Oligocene and Lower Miocene yield but scanty fish remains. The occurrence in Europe of Amia (Xofaeus) and Lepidosteus is noteworthy. The Middle Miocene Molasse of Switzerland, Swabia (Baltringen), and Upper Bavaria, the marine deposits of the Vienna basin, the valley of the Rhine, and the Aquitaine basin sometimes contain an abundance of fish remains, among which the teeth, dermal plates, and spines of sharks, rays, and chimaeras, the vertebrae, teeth, and scattered bones of Teleostei are especially common. With few exceptions these remains are referable to recent genera. The brackish-water clay of Unterkirchberg, near Ulm, the freshwater marl of Oeningen and Steinheim, the Sarmatian deposits of Badoboj and other localities in Croatia, and the Cerithium marl of the Vienna basin, also show that at the time of their formation the fish fauna of the fresh and brackish waters of Germany was not very different from that still surviving in southern Europe and Asia Minor. The remarkably rich Upper Miocene fauna of Licata in Sicily exhibits a mixture of marine and freshwater fish remains, which is also partially notice- able in the neighbourhood of Girgenti, in the gypseous marls of Sinigaglia, near Gabbro in Tuscany, Lorca in Spain, and Oran in Algeria. In his mono- VOL. II I 114 AMPHIBIA class ii graph of 1873, Sauvage describes 52 species from Licata, and of these 44 are of marine origin. The character of this fish fauna is essentially Mediterranean, but without exception the species are extinct. So far as fishes are concerned, there is scarcely any noteworthy difference between the Pliocene fauna and that of the present day. The distribution of fishes in time affords many facts illustrating the development of this class. In the Palaeozoic epoch there were only Selachii, Holocephali, Dipnoi, Ostracodermi, and Ganoidei ; the Selachii and Ganoidei, indeed, appearing together in the Silurian. These two main divisions of the phylum of fishes must thus have become separated very early, if indeed they originated from a common stock. Fossils beginning in the Old Red Sandstone, and ranging through all later formations, prove that the Holocephali had already diverged from the Selachii in Palaeozoic times, and the branch has been preserved with its partially embryonic characters (polyspondyly, autostyly) until the present day. The origin of the Dipnoi is quite obscure. Their Palaeozoic representa- tives agree in many respects with the Crossopterygii. As, moreover, the Dipnoi also share important characters with the Holocephali, it seems probable that the Holocephali, Dipnoi, and Ganoidei arose from a common stock. So far as the development of the internal skeleton is concerned, the Ostracodermi and Arthroclira are quite primitive. Their origin is wholly unknown. Among the Ganoids the Crossopterygii form an isolated group, well separated from the other orders both phylogenetically and systematically, having its last survivors in the modern Polypteridae, and probably more closely related to the Dipnoi and Amphibia than to the other Ganoids. The Hetero- cerci, Lepidostei, and Amioiclei form a closely connected group of Ganoids. It has already been remarked that the first order not only precedes the Lepidostei in time, but is also probably ancestral to them. The Amioids may have diverged from the Lepidostei during the Triassic or Jurassic period. The Teleosteans are merely a great lateral branch of the Ganoids. It is, however, improbable that they are of monophyletic origin ; for although the Clupeoids are the ancestral group of most of the Physostomi, which have arisen from the Mesozoic Amioids, other families even on their first appearance seem to be so remotely allied to Clupeoids that a different origin must be sought for them. The Physoclysti are indeed only derivations of the Phvso- stomi differentiated in various directions. [The section Pisces has been translated and revised by Dr. Arthur Smith Woodward, of the British Museum, who has attempted to bring the subject up to date, while preserving in the main the author's methods and principles of classification. — Ed.] Class 2. AMPHIBIA. Amphibians and Batrachians. 1 Cold-blooded vertebrates, aquatic or terrestrial in habit, usually naked, but some- times with a corneous or osseous dermal covering ; respiration' both branchial ami pulmonary in early stages, and in some forms gills remain functional throughout life. Development by metamorphosis, but without amnion and allantois. Skull with two occipital condyles. Bibs never attached to sternum. Limbs adapted for ambulation or natation, never in the form of fins, and rarely absent. 1 Hoffmann, C. K., Die Amphibien. Bronn's Classen und Ordnungen des Thierreiclis, vol. VI. pt. 2. 1873-78. — Wcujner, J., Natiirliches System der Amphibien, 1828-33. phylum viii . VERTEBRATA 115 In external appearance amphibians more nearly resemble reptiles than fishes. The body is generally elongate, and terminates as a rule in a well- developed tail, although some small forms (Anura) are ecaudate. Among recent amphibians limbs are wanting only in the Coecilians (Gymnophiona). Certain extinct Stegocephalians (Aistopoda) appear also to have been com- pletely apodal ; but elsewhere two pairs of limbs are invariably present, the anterior usually terminating in four digits and the posterior in five. Recent amphibians are naked with the exception only of the Coecilians, which are covered with small scales arranged in transverse rings. The fossil Stegocephalians usually have a scaly armature on the ventral surface, and sometimes on the dorsal as well. The number of vertebrae in the spinal column is extremely variable (10-150), depending upon the length of the body and especially the tail. Cervical, dorsal, sacral, and caudal regions are distinguished. The most primitive form of vertebrae occurs in the Palaeozoic Stego- cephalians, where the notochord is enclosed by thin cylinders of bony tissue, or by separate pleurocentra and hypocentra, as in early Ganoids. Where the column is more completely ossified, three types of vertebrae are exhibited. The first, or amphicoelous, is biconcave ; the procoelous has the anterior vertebral face concave and the posterior convex ; and in the opisthocoelous type the anterior face is convex and the posterior concave. The cervical region comprises but a single vertebra, the atlas, although this probably corresponds to both atlas and axis of higher classes. Its con- cave anterior face receives the bony or cartilaginous occipital condyles, and is often provided with a spatulate, forwardly directed basal process. Each of the dorsal vertebrae supports a neural arch (new •apophysis), which becomes earlier and more completely ossified than the centrum, and may be either suturally united or anchylosed with the latter. The two halves of the neural arch unite above to form a more or less strongly developed spinous process (spina d or sails) ; and they bear anteriorly and posteriorly a pair of oblique articular processes (processus obliqui, zygapophyses), the forward pair of each vertebra overridden by the hinder pair of the next in front. The neural arch also supports, as a rule, a pair of transverse processes (diapophyses) for the attachment of ribs. When the latter are double-headed, as is often the case, another and shorter lateral process (par apophysis) is developed by the body of the vertebra. The sacral region is also formed by a single vertebra, which supports the pelvis, the latter being attached either directly by means of exceptionally stout transverse processes, or by sacral ribs, usually of peculiar form. Haemal arches (haemapophyses, "chevron bones") are commonly borne by the caudal series, the foremost of which sometimes have ribs attached to the transverse processes of the neural arch. The entire series of caudals in the Anura is fused into a single elongate piece called the coccyx. The primordial cranium remains partly cartilaginous throughout life, and is partly replaced by bony pieces, which are either direct ossifications of the cartilaginous capsule (exoccipitals, auditory capsules, quadrate, sphen-ethmoid), or are investing bones (parietals, frontals, nasals, vomer, parasphenoid). The basioccipital and supraoccipital usually remain small cartilaginous tracts ; but save in certain Stegocephalia and a few other forms, the exoccipitals are completely ossified, and bear the articular condyles. The exoccipitals are of considerable 116 AMPHIBIA class ii size, and enter into the border of the tympanic region. The latter is roofed by several small bones corresponding to the prootic and opisthotic of fishes, or these may unite into a single element called the petrosal. The antero-lateral walls of the skull remain cartilaginous ; but in the ethmoidal region an ossifi- cation takes place, forming the orbitosphenoid which is usually separate, but sometimes {Anura) fuses with the median elements to form a single ring- shaped bone (sphen-ethmoid). The cranial roof is formed by the paired parietals, frontals, pre- and post- frontals, and nasals; and in Stegocephalians there are present in addition the so- called supratemporals, squamosals, postorbitals, and lachrymals. The palate is formed as in fishes by a large median parasphenoid, and usually paired vomers, and palatines. There is no movable suspensorium for the lower jaw ; the cartilage representing it unites with the squamosal above, and quadrato-jugal below. Sometimes an ossified quadrate is formed at the end of the suspen- sorial cartilage. Attached to the quadrato-jugal in front are the maxillae, and anterior to these the premaxillae, which complete the rim of the upper jaw in front. Many of the Urodeles have the maxillae and quadrato-jugal replaced by connective tissue. Between the quadrate and parasphenoid is placed the pterygoid, usually a trifid bone which joins the parasphenoid by its shorter arm, while its anterior branch forms the outer border of the palatal vacuity. The palatines, when present, usually join the anterior ends of the pterygoids, and extend parallel with the maxillae. The mandibular ramus is composed of three or four elements, as in fishes. The visceral skeleton is formed by the paired hyoid bones, and, in gill-breathers, by three or four partially ossi- fied branchial arches. The teeth are acutely conical, and are commonly borne by the mandible, maxillae, premaxillae, vomer, and palatines. Rarely the parasphenoid and pterygoid are armed with minute teeth, and only certain Anura are edentulous. Teeth of the acrodont type have their bases implanted directly upon the rim or top of the jaws ; those of the pleurodont type are sunk against the inner side of the jaws. As in Ganoids and bony fishes, worn teeth are not replaced by successional ones developed beneath them, but new ones are formed independently alongside the old, and gradually oust the latter as their basal parts become reabsorbed. Amphibian teeth differ from those of fishes chiefly in the absence of vasodentine ; and the spacious pulp cavity which during life contains vascular or connective tissue, occurs in the fossil state either hollow or impregnated with mineral matter. Some Stegocephalians have complex or " labyrinthodont " teeth, the dentine being strongly folded, as in certain Crossopterygian fishes. In the pectoral arch the scapula is ossified in at least its proximal portion, where it joins the coracoid and pre-coracoid, and forms the articular face for the humerus. A bony sternum is usually absent. Stegocephalians are peculiar in possessing between the pectoral limbs one median and two paired exoskeletal plates, commonly regarded as interclavicle and clavicles. The fore-limb is composed of the usual bones, humerus, radius, and ulna ; a carpus which is either cartilaginous or consists of two rows of ossicles ; and three, four, or five metacarpals which support digits with from one to four phalanges. The pelvic arch is composed of a long and slender bony ilium, which is attached either directly to the transverse process of the sacral vertebra, or to order i STEGOCEPHALIA 117 the sacral ribs, and is directed obliquely downward ; a flattened, sometimes discoidal bony ischium ; and a cartilaginous or ossified pubis lying imme- diately in advance of the ischium. The ilium and ischium usually take part together in the formation of the acetabulum, which receives the femoral head. In the Anura the tibia and fibula are fused. The tarsus is cartilaginous or com- posed of several small ossicles, and the pes resembles the manus, except that it is usually pentadactyle. Four orders of Amphibians are recognised as follows : — Stegocej>hidin, Gymno- phiona, Urodela, and Anura. Order 1. STEGOCEPHALIA. 1 Salamander or lizard-like caudate amphibians, the cranial roof and whole of the cheek >'<>irred with plates ; cranial roof posterior to the orbits formed by two pairs of median and two pairs of lateral elements ; pineal foramen always occurring in the parietal. Teeth sharply conical, with large pulp cavity, and walls sometimes highly complicated by infolding of the dentine. Vertebrae consisting either of simple cylinders, or of separate pleurocentra and hypocentra, or of completely ossified amphi- coelous centra. Three exoskeletal plates present in the thoracic region, interpreted as clavicles and inter clavicle. Usually a ventral and sometimes a dorsal armowing of small overlapping sccdes. The Stegocephalians range from the Carboniferous to Upper Trias, and comprise the largest known amphibians. A tail is invariably present, and in most cases, two pairs of limbs ; only a few genera are apparently destitute of appendages. Unlike recent amphibians, most Stegocephalia possess a well-developed dermal armour of bony scales or scutes, which almost always covers the ventral sur- face of the body, and sometimes extends to the under side of the limbs and back as well. Dorsal scales, however, are thinner than the abdominal, and are usually round or oval. The ventral scutes are sometimes thickened, and always arranged in regular series. The abdominal series form oblique rows meeting at a sharp angle along the median line, but those covering the thoracic, pectoral, and caudal regions, and under side of the limbs are arranged in different patterns. The scales are of true bony tissue, and vary considerably 1 Literature : Ammon, L. v., Die permischen Amphibien der Rheinpfalz. Munich, 1S89. [Extensive 1 »il »lio- graphy.] — Bavr, G., The Stegocephali : a Phylogenetic Study (Anat. Anz. vol. XI. No. 22), 1896. — Broili, F., and Stickler, L., Ueber Eryops megacephalus Cope (Palaeontogr. vol. XLVL), 1899.— Bwmeister, H., Die Labyrinthodonten aus deni bunten Sandstein von Bernburg. Berlin, 1840.— Die Labyrinthodonten aus dem Saarbriicker Steinkohlengebirge. Berlin, 1S50. — Ojj><\ E. ])., Synopsis of the extinct Batrachia and Reptilia of North America (Trans. Amer. Phil. Soc. vol. XIV.), 1869.— /&/.. Die Organisation von Archegosaurus (Zeitschr. deutsch. geol. Ges. vol. XLVIIi.). 1896. — Ueber die Korperform und Haut bedeckung von Stegocephalen (Setzber. Ges. naturf. Freunde, Berlin), 1896. — Meyer, II. v., Zur Fauna der Vorwelt, pt. 2. Frankfort, 1847. — Ueber den Archegosaurus (Palaeontogr. vols. I., VI. XV.), 1851, 1857, 1866. — Idem, and Plienenger, T., Beitrage zur Palaeontologie Wurttembergs. Stuttgart. 1S44. — Miall, L. C, Report on the Structure and Classification of the Labyrinthodonts (Rept. Brit. Assoc 42nd and 43rd Meet.), 1874-75. 118 AMPHIBIA CLASS II in form, the more common varieties being oval, rhomboid, oblong, fusiform, or rod-shaped (Fig. 193). The vertebral column usually remains in an embryonic condition, and recalls that of Ganoid fishes. The degree of persistence of the notochord is very variable, but only the most specialised genera have it completely A 2b i — .V Fig. 194. Phyllospondylous vertebrae of Branchiosaiirus arnhlystomus, Credner. Enlarged (after Credner). ch, Notochord ; n, Neural arch ; sp, spinous process ; d, transverse process ; z, Zygapophysis. Fig. 193. A, Ventral armour of Branchiosaiirus. B, Scutes of Branchiosaiirus; C, of Hylonomus; D, of Pelosaurus ; E, of Archegosaurus ; F, of Sclerocephalus ,■ G, of Disco- saurus ; H, of Petrdbates (after Credner). Fio. 105. Lepospondylous vertebrae of Hylonomus. ch, Noto- chord replaced by mineral matter ; k, Bony cylinder of the centrum ; c, Rib (after Credner). interrupted by ossification of the centra ; in the Branchiosauria it is com- pletely persistent. Ossification of the vertebral column is least complete among the Phyllo- spondyli (Fig. 194), where, in the absence of pleurocentra, the neural arch itself extends down- ward and joins with a pair of delicate hypocentra (or intercentra) to enclose the notochord and to form transverse processes for support of the ribs. In the Leposponch/li (Fig. 195) the notochord is persistent and encased in constricted bony cylinders, which are hourglass-shaped in longi- tudinal section. In some genera, however, the continuity of the chord is all but interrupted by ossification of the middle portion of the centra. The Temnospondyli (Fig. 196) have the ver- tebrae composed of several distinct pieces. Rhachitomous dorsal vertebrae of Ossification begins with the neural arch, whose Archegosaurus. sp, Spinous process: i i • , , c . i -i , 1 z, z', zygapophyses ; n, Neural arch- halves remain separate at first, but later coalesce gw^Hypocentrum • pic, pieurocen- anc ] are continued above into a stout and some- times distally thickened spinous process. The centra may be either rhachitomous or embolomerous. Those of the rhachitomous type are formed by a horseshoe-shaped basal piece (hypocentrum or inter- Fig. 196. ORDER I STENOCEPHALIA 119 Fig. 197. Rhachitomous caudal vertebrae i>t' Archegosaurus. Lettering as in Fig. L96. centrum, the tapering extremities of which are directed upward), and a pair of lateral pieces, or pleurocentra ; a structure which is paralleled in certain Ganoids (cf. Fig. 121). The hypocentrum usually ossifies in advance of the pleurocentra, and lies directly underneath the neural arch. Occasionally a small horizontal basal piece is inserted beneath the pleurocentra and between the hypocentra. This piece, according to von Meyer, appears to be divided in the anterior caudals of Archegosaurus (Fig. 197). The rhachitomous type of vertebrae passes over into the embolomerous when the pleuro- centra unite with the hypocentrum to form a complete bony ring, which coossifies with the neural arch above (Fig. 198). Or occasionally the crescentic intercentrum develops into a com- plete ring, and the pleurocentra unite with each other below and the neural arch above to form a second ring. Some genera (Cricotus) have rhachitomous dorsal, and embolomerous caudal vertebrae. The most advanced stage of vertebral ossification occurs among the Labyrinthodonts, where the centra are solid bony discs, slightly amphicoelous ; sometimes they are pierced for the passage of the notochord (Fig. 199), or a channel is visible below the neural canal through which it extended (Stereospondyli). There is usually but one cervical vertebra, the atlas, which is concave in front and facetted to receive the exoccipital condyles, but bears neither ribs nor anterior zygapophyses. Most or all of the presacral or dorsal series bear ribs, which may be either single or double-headed. The single sacral vertebra is provided with a pair of stout transverse pro- cesses for the attachment of sacral ribs. Haemal arches (haemapophyses, " chevron bones") are borne by the caudal series, being joined to the centrum (pleurocentrum) or intercentrum. The cranium (Fig. 200) exhibits the depressed, broadly triangular form characteristic of amphibians, but is invested by bony plates which form a very different pattern from the usual amphibian type, while resembling in some respects those of Ganoids and Crocodiles. The cranial plates are usually ornamented externally with radiating sculpture, pittings, or punctae, and sensory canals are often conspicuous. The cranial roof is pierced by several apertures, the f° > Huxley largest of which are the orbits, and around them there is often a sclerotic ring. The anterior nares are placed close to the border of the snout, and separated from each other by a considerable interval. Another and smaller opening occurs at the median suture between the parietals, corresponding in position to the so-called parietal foramen of Lizards. Fig. 198. Embolomerous vertebrae of Diplovertehr&n punctatum, Fritsch. Lower Permian ; Bohemia, 1/] (after Fritsch ). Fig. L99. Dorsal vertebrae of 120 AMPHIBIA CLASS II Pmx Anterior Supratemporal ; Ju, Jugal The thin, flat bones constituting the cranial roof are of dermal origin, as in the case of cartilaginous Ganoids. The brain cavity is protected by the large, paired parietals, posterior to which are two pairs of supra- temporals, the outermost being the larger and forming the hinder border of the auditorv notch. The inner or median pair of supra- temporals are commonly described as supraoccipitals (so), and the outer or lateral pair as " epiotics " (ep), although clearly of dermal origin. The plate anterior to the epiotic is usually called the squamosal (sq), and in front of this lie the post- orbitals (par) and large, posterior cheek plate (st), which is also iden- FlG - - oc - titled with the supratemporals. The Dorsal aspect of the skull of MeianerpetOn pulcherrimum, , , , pf i „„:,.„ tno-Prripr with Fritsch. Restored. 1/1 (after Credner). A, Orbit ; Pmx, TiWO last-named pailS, tOgetner Vv 1IP1 PremaxiUa ; Mz, Maxilla; Na, Nasal ; Prf, Prefrontal ;Fr t ^ e s0 . ca H ec l epiotics, are wanting in Frontal; Ptf, Postfrontal; Pa, Parietal ; Por, Postorbital ; I ; o_ Sq, Posterior squamosal ; Ep, Epiotic ; St, So, all modern amphibians. Anterior to the parietals and between the orbits is a pair of usually elongate narrow frontals, and anterior to these a pair of large nasals with openings for the external nares at their an tero- lateral angles. A pair of curved dentigerous premaxillae (pmx) terminate the snout in front. The frontals rarely enter into the border of the orbits. These openings are usually bounded behind by the post- orbital and postfrontal, the latter plate being invariably present ; mesially by the postfrontal and prefrontal ; and exteriorly by a long cheek plate called the jugal. Very often a narrow tri- angular bone, the lachrymal, is inserted between the prefrontal and jugal, but is usually pushed forward in advance of the orbit. The postero- inferior cranial angle is formed by the quadrato- jugal, which sometimes develops a pro- cess on the under side for articulation with§ the lower jaw. In some of the larger Stegocephalians the distal end of this process is separated off* from the quadrato- jugal by a suture, and forms a distinct quadrate bone. Joining the quadrato- jugal in front is the maxillary, a long, narrow, gently curved bone, which completes the outer border of the cranium as far as the premaxillae. Most Palaeozoic Stegocephalians had the basiocciput cartilaginous, but in the Labyrinthodonts and certain other forms the supratemporals are followed CUJ" Fig. 201. Palatal aspect of the skull of Branehiosaurus. Re- stored. 2 /i (after Credner). Pmx, PremaxiUa ; Mx, Maxilla; QuJ, Quadrato-jugal ; Ft, Pterygoid; PSj>h, Presphenoid ; PI, Palatine ; Vo, Vomer. ORDER I STEGOCEPHALTA 121 by a pair of obliquely inclined bony exoccipitals, which bear the articular condyles. The under side of the cranium is remarkable for the large size of the palatal vacuities, and great development of the parasphenoid, which expands posteriorly into a broad, thin plate. It extends forwardly as a long, slender process, and unites with the relatively large-sized vomer, the latter element being paired in the earlier, unpaired in the later forms. The vomer usually joins the j>remaxillae anteriorly, and is bounded exteriorly by the maxillae, the internal nares, and front portion of the palatines. Its broad, flat surface is either edentulous or set with minute teeth, but occasionally one or two powerful tusks are present in front of the narial openings, and there is a series of smaller teeth bordering the anterior and lateral edges of the vomer. The posterior expansion of the parasphenoid unites with a trifid bone, the pterygoid. The short inner arm of the latter in fact often envelops the parasphenoid ; its long, forwardly directed process extends parallel with the palatine and maxilla, forming the outer border of the palatal vacuity ; and its short posterior branch unites with the quadrato-jugal and limits the temporal vacuity. The palatines lie between the vomer and anterior extremities of the pterygoid. They are bordered externally by the maxillae, as a rule, and anteriorly by narial openings. They frequently bear a series of small teeth. The lower jaw (Fig. 227) of all Stegocephalians extends the full length of the skull, and in consequence the gape of the mouth is very wide, as r in Anura. The mandibular ramus is composed of three pieces, of which the dentary forms the tooth-bearing anterior portion, and the angular the lower portion ; behind the dentary and above the angular is the articular, which bears a deep trans- verse articular facette terminated behind by an elevated process. Superimposed on these three pieces on the inner side of the jaw is a membrane bone called the splenial (or opercular). Teeth occur in regular series, decreasing in size posteriorly • and sometimes one or two greatly enlarged teeth occur at the symphysis. The union of the two rami in front was , probably ligamentous in most cases. The teeth x of the smaller Palaeozoic Stegocephalians are smooth, slender, hollow, and conical (Fig. 202), and implanted either directly in the supporting bone, or attached by a cement - base. Verv often the lower half or two-thirds of the crown is ex- ternally grooved or striated, in which case a radial infolding of the dentine extends for an equal height (Fig. 203). xr n l .• it Vi- B, Enlarged (after Credner). .Numerous fine dentine tubules Fig. 202. Lower jaw of Branehiosaui us with simple, smooth teeth. A, Fig. 203. larged. 1, Outo surface! & b, extend downward toward the periphery, and tangen- Lowerhaif'with a portion broken fc j a u y to t h e wa u s f t h e radial prolongations of the away to show the folded dentine. * l & pulp cavity. In the more complicated teeth, secondary and even tertiary branching of dentine tubules may occur, and at the same time undulating or tortuously folded layers of cement, such as covers the exterior of the tooth, may become intercalated between the bundles of dentine 1 x Credner, H., Zur Histologic der Faltenzahne palaeozoischer Stegocephalen (Abhandl. sachs. Ges. Wiss. vol. XX.), 1893. 12-2 AMPHIBIA CLASS II tubules. This gives rise to the highly characteristic " labyrinthodont " structure, which reaches its extreme development among the larger and geologically later Stego- cephalians (Fig. 204). The internal structure becomes progressively less compli- cated toward the apex of the tooth, above the zone where radial infoldings of the walls leave off, the dentine is traversed simply by straight tubules radiat- ing from the pulp cavity. The insertion of the teeth may be of the acrodont or pleurodont type, as already described, or they may be seated in shallow alveoli. Traces of branchial arches being conspicuous in the young of several Palaeozoic genera, the sup- position is natural that respiration was by gills during the early stages of all Stegocephalians. is of unique construction, The most Fig. 204. Cross-section of a tooth of Mastodonsaurus jaegeri. % (after Owen). P, Pulp cavity ; c, Dentine tubules. The Stegocephalian pectoral arch (Fig. 205) differing from that of other amphibians in notable respects characteristic, as well as the largest and usually best preserved bones, occupy an ex- ternal position on the thorax between the pectoral limbs. These b@nes are three in number, and as a rule prominently sculp- tured. The median element identified as the interclavicle (or entosternum) varies considerably in form and size amongst different genera. Most frequently it is rhombic, but sometimes transversely oval, and may terminate behind in a long median extension. Partly overlapping the forward portion of the interclavicle are the paired plates which correspond to the clavicles of other amphibians. Their posterior ends are slender and slightly curved upwards ; the anterior end is expanded into a triangular or oval plate, often sculptured, but sometimes smooth as if it Fig. 205. A, Pectoral arch of BrancMosaurus. />', Melanerpeton (after Credner). id, Interclavicle; d, Clavicle ; co, Coracoid ; sc, Scapula [ = cleithrum of Gegenbaur]. ORDER I STEGOCEPHALIA 123 had been embedded in the integument. A flat, semicircular, or lunate plate, interpreted as the coracoid, is placed at a slight distance behind the clavicles, and there is also a narrow or rod-like piece with expanded distal extremities, corresponding to the scapula of other groups. [Gegenbaur, and following him G. Baur, interpret these bones differently, holding that the coracoid was in all probability cartilaginous, and identifying the bone commonly known by that name as the scapula, and the so-called scapula as the cleithrum. The latter, as shown by Gegenbaur, was attached to the distal end of the clavicle.] The bones of the appendicular skeleton, so far as known, agree in form, number, and arrangement with those of living Urodeles. The humerus is rarely furnished with articular condyles, its extremities remaining as a rule cartilaginous. Ulna and radius are always separate, simple, more or less elongate, and without articular faces. The carpus is imperfectly known ; in many Palaeozoic genera it appears to have been cartilaginous, in others partly ossified. The metacarpals and phalanges are slender and elongate. The pelvic arch (Fig. 206) is strongly developed, but seldom so well pre- served that the form and position of all the parts are clearly distinguishable. The ilium is short, stout, somewhat ex- panded at the extremities, and attached to the sacral ribs. Ischium and pubis sometimes unite to form a single large plate (ischio- pubis), or they may remain separate. The inner edges of the ischia form a sym- physis in the median line. The pubes, which are smaller, sometimes remain car- tilaginous amongst Palaeozoic forms. The hind-limb is almost always more strongly developed than the fore-limb. The femur is a strong, elongate bone, without an ossified capitulum, but often with well-formed distal condyles. Tibia and fibula remain separate, and resemble the corresponding bones of the anterior limb. The tarsus is either cartilaginous or composed of two rows of small bones. The pes is provided with five digits, but is otherwise closely similar to the manus ; sometimes the second digit is the longest, in other cases the third. Habitat. — The mode of occurrence of Stegocephalians in the Coal Measures, Lower Permian, and Keuper, indicates that they were either freshwater inhabitants, or terrestrial forms. Some of the smaller genera appear to have sequestered themselves in hollow tree-stumps, since in Nova Scotia, at least, Fig. liOG. Pelvic arch of Mastodonsaurus gigantem I, Ilium ; Isrh, Ischium ; Pu, Pubis : , Jaeg. (after Fraas). Ac, Acetabulum. their remains are commonly found in cavities of decayed Sigillaria and 124 AMPHIBIA CLASS II Lepidodendron trunks. The larger forms, some of which attained gigantic size, were predatory, and probably subsisted on other amphibians, fishes, and crustaceans. Sub-Order A. PHYLLOSPONDYLI. Credner. (Branchiosauria.) Notochord persistent and encased in imperfect barrel-shaped vertebrae formed by a pair of delicate hypocentra and downward prolongations of the neural arch, but without pleurocentra. Teeth simple, hollow. Family 1. Branchiosauridae. Fritsch. Lizard -like Stegocephalia with broad, obtusely rounded heads. Basiocciput cartilaginous, and also the carpus, tarsus, and pubis. Bibs short and straight, with simple, thickened proximal ends. Pubis not ossified. Ventral scales thin, small, pointed, and arranged in regular series. Carboniferous and Permian. Branchiosaurus, Fritsch (Protriton, Pleuroneura, Gaudry), (Figs. 201, 202, 205 Body 15-20 mm. long. B Head about as broad as long, truncate behind, with shallow auditory notch, and very large elliptical orbits. Sclerotic ring of about 30 small plates, and also a supplementary series of smaller /Xfv 1 m m it Fig. 207 Branchiosaurus amblystomus, Credner. Rothliegendes, Niederhasslich, near Dresden. A, Skeleton of adult indi- vidual, i/j. B, Restoration of a larval form with gill arches (after Credner). i" IU. -VO. Branchiosaurus petrolei, Gaudry sp. Lower Permian ; Autun. Vi (after Gaudry). plates irregularly arranged. Cranial plates radially striated or punctate. Parasphenoid greatly expanded behind, and uniting with trifid pterygoid. Vomer paired, the two pieces triangular ; palatines imperfectly known. Jaws with a single series each of slender, closely spaced conical teeth. Inter- clavicle sub-rectangular, externally furrowed. Ilium stout, hourglass-shaped ; ischium delicate, triangular. The entire ventral surface of the body, together with a portion of the tail and limbs, was protected by deeply overlapping cycloidal scales (Fig. 193) arranged in order i STEGOCEPHALIA 125 several distinct series. Those of the thoracic region form transverse rows ; those of the pectoral region oblique rows converging posteriorly toward the median line ; those of the abdominal region oblique rows, converging at a lesser angle in the opposite direction ; and those of the under side of the tail and legs form slightly curved trans- verse rows. Functional gill arches are indicated in many immature examples by the regular series of minute denticles which were originally arranged on them. Tail known to have been about as long as trunk with the head, but most of the caudals unossified. This genus and Archegosaurus furnish the commonest and best known examples of Palaeozoic Amphibians. Remains of Branchiosaurus are abundant in the fine- grained limestone of the middle Rothliegendes, near Dresden, where the small bones are clearly outlined in white against a grayish -coloured matrix. Credner's elaborate researches on the structure and development of this form were based on comparisons of over 1000 specimens. Several species occur also in the Lower Permian of Niirschan (Nyran) and Kunova in Bohemia, and Oberhof and Friedrichsroda in Thuringia. Pelosaurus, Credner (Fig. 193, d). 18 to 20 cm. long. Skull relatively very large, with lachrymal in front of orbits, and no supplementary sclerotic plates. Lower Permian ; Niederhasslich, near Dresden. P. laticeps, Credner. Melanerpeton, Fritsch (Figs. 200, 205, b). 2*5 to 13 cm. long. Skull as in Branchiosaurus, but more produced posteriorly, and squamosal divided (sq and x). Interclavicle extended into a long posterior process. A distinct dermal armouring not present, but quantities of small calcareous shagreen -like particles sometimes observed instead. Branchial arches present in young examples. Lower Permian of Braunau, Bohemia ; Lhotka, Moravia ; and Niederhasslich, Saxony. Dawsonia, Fritsch. Jaw-bones, vomer, palatines, and parasphenoid armed with teeth. Lower Permian ; Bohemia. Amphibamus, Cope ; Pelion, Wyman. Coal Measures ; Linton, Ohio. Sub-Order B. LEPOSPONDYLI. Zittel. (Microsauria.) Notochord persistent and enclosed in constricted bony cylinders, hourglass-shaped in longitudinal section. Teeth simple, conical, hollow. Family 1. Microsauridae. Dawson. Salamander or lizard-like, usually longicaudate Stegocephalw . Fore-limbs less robust than the hinder pair, carpus and tarsus ossified or cartilaginous. Ribs long and slender, curved, generally double-headed. Pubis ossified. Ventral, and in rare cases also the dorsal surface covered with small, round, oblong, oval or oat -shaped scales. Carboniferous and Permian. Hyloplesion, Fritsch. Cranial bones smooth, finely striated or punctate. Orbits large, with sclerotic ring. Tarsus ossified. According to Fritsch, both dorsal and ventral armatures were present, composed of overlapping oval scales with thickened fig, 209. posterior border. Lower Permian : Nurschan, Bohemia, and ^, vertebra, and i T . -i i .. i. i c\ B, Rib of Hylonom us JNiederhaSSllcn, baXOny. lyelli, Dawson. Coal Hylonomus, Dawson (Fig. 209). Small and imperfectly xo^coVia J ° ggins ' known, perhaps identical with the preceding. Coal Measures ; Nova Scotia. Other allied American genera are Amhlyodon, Dawson ; 6 126 AMPHIBIA CLASS II Hijlerpeton, Owen • and Brachydectes, Cope, all small and fragmentary preserved. SeeUya, Fritsch. Larval, lizard-like forms under 2*5 cm. in length, with rounded snout. Teeth smooth, simple, hollow, present on all bones of the palate, those of the premaxillae much larger than the maxillary teeth. Parasphenoid a long slender bone ex- panding behind into a rectangular plate. Gill arches, and both dorsal and ventral armour present. Scales elongated oval, ornamented with undulating or dichotomis- ing lines. Very rare in Lower Permian of Niirschan, Bohemia. S. pusilla, Fritsch. Bicnodon, Orthocosta, Microbrachis, Limner- peton, Fritsch. Lower Permian ; Niirschan, Bohemia. Tuditanus, Cocytinus, Colosteus, Lepto- phrcCdus, Pleuroptyx, Cope. Coal Measures ; Linton, Ohio. Lepterpeton, Huxley (Fig. 210). Lizard- like, longicaudate, with narrow, elongated head and tapering snout. Orbits midway the length of the skull ; carpus and tarsus cartilaginous. Hind-limb slightly stouter than the anterior, rhombic. Coal Ireland. Keraterpeton, Huxley (Ceraterpetum, Huxley). Salamander - like, with much elongated tail ; total length upwards of 50 cm. Skull broad, rounded anteriorly, orbits far forward, and external bones sculptured. A pair of large, backwardly directed horns firmly attached to the postero-lateral cranial angles. Very small ventral scutes, and no dorsal armour. Coal Measures ; Kilkenny, Ireland, and Linton, Ohio. Scincosaurus, Fritsch (Fig. 211). Skull smaller in proportion to the body than in Keraterpeton, with more numerous pre- sacral vertebrae, and distinct ossifications in carpus and tarsus. Lower Permian ; Bohemia. S. crassus, Fritsch. Urocordylus, Huxley and Wright (Oestocephalus, Ptyonius, Cope), (Fig. 212). Body and tail elongate, total length about 50 cm. Fore-limb slightly less developed than the hind, both pentadactyle. Skull depressed, triangular, posteriorly truncate. Orbits forwardly situated. Tail nearly twice as long as the trunk with the head. Caudal vertebrae about 80 in number, with long neural and haemal spines, expanded and crenulated distally. Ventral armour composed of upwards of 100 rows of scutes converging toward the median line, in form elongated oval, fusiform or oat-shaped. Coal Measures ; Ventral scales elongated Measures ; Kilkenny, Fig. 2iu. Lepterpeton dobbsii, Huxley. Carboniferous Kilkenny, Ireland. 3/ 4 (after Huxley). ORDER I STEGOCEPHALIA 127 Kilkenny, Ireland. Lower Permian ; Niirschan, Bohemia. U. scalaris, Fritsch. Acanthostonia, Credner (Fig. 213). Skull 25-35 cm. long, sharply para- bolic in outline, externally pitted. Orbits relatively small, rounded, placed Fig. 211. Keraterpeion erassum, Fritsch. Lower Permian ; Niirschau, Bohemia. Restored. 1/1 (after Fritsch). Fig. 212. Urocordyhis wandetfordii , Huxley. Coal Measures; Kilkenny. Ireland. Caudal vertebrae, V] (after Huxley). Qui! Fig. 213. Palatal aspect of skull of Acanthostonia vorax, restored. Vi (after Credner). .1, Orbit; N, Internal nares ; Pmx, Pre- maxilla ; Mx, .Maxilla; Qui, Quadrato- jugal ; PSph, Parasphenoid ; /'/. Ptery- goid. in posterior half of the skull, and with sclerotic ring. All bones of the buccal cavitv set with teeth. Lower Permian ; Saxony. Family ±. Aistopodidae. MialL (Aistopoda.) Body serpentiform, without either limbs or arches for their support. Vertebrae constricted amphicoelous cylinders. Teeth simple, conical, hollow. l!i l >s slender, with one or two processes. Carboniferous and Permian. 128 AMPHIBIA CLASS II 'mx Dolichosoma, Huxley (? Phlegethontia, 1 Molgophis, Cope), (Fig. 214). Skull relatively small, triangular, with tapering snout ; external bones smooth, and median ones more or less fused. Premaxillae very small. Over 150 vertebrae, and total length upwards of 1 m. Neural spines atrophied. Eibs slender, the foremost ones angularly bent, later ones straight. Dermal armature not observed. Coal Measures ; Kilkenny, Ireland. Lower Permian ; Bohemia. Ophiderpeton, Huxley (Fig. 215). Skull imperfectly known, shorter and more obtuse than in Dolichosoma. Ribs slender, resembling inter- muscular bones of fishes, with dorsal and ventral processes. Ventral scutes small, oat- shaped ; dorsal ossicles sha- green-like. 0. brownriggi, Huxley, from the Irish Coal Measures, 40-60 cm. long. Five smaller species known from the Permian of Bohemia. Dolichosoma Lower Permian Restored. 3/ 1# Fig. 214. longissimum, ; Niirschan, Fritseli. Bohemia. 215. Ophiderpeton granu- losum, Fritsch. Rib. 6 /l. Permian ; Bo- hemia, d, Dorsal ; v, Ventral process. Sub-Order C. TEMNOSPONDYLI. Zittel. Vertebrae composed of several pieces, usually of the rhachitomous type, sometimes embolomerous. Basioccipital region usually, and carpus and tarsus always ossified. Teeth with radially infolded walls. Carboniferous to Lower Trias. Archegosaurus, v. Meyer (Figs. 196, 203, 216, 217). Total length up- wards of 1*5 m. Skull in the young obtusely triangular, scarcely longer than broad, but becoming greatly elongated in the adult, with broad, anteriorly rounded snout. External bones radially sculptured, sensory canals feebly marked. Orbits situated in about the middle of the skull in the young, and in hinder portion in mature individuals ; sclerotic ring of 20-23 plates. Anterior nares elongate. Postorbitals triangular, supratemporals large, lachrymals long and narrow, basioccipital region not ossified, palatal vacuities large. Parasphenoid and pterygoids toothless, vomer with one or two pairs of relatively large teeth, and maxillae, premaxillae, and palatines each with a single series of teeth. Dentine deeply and simply folded in lower half of the crown. Denticles of branchial arches observed in young individuals. In the caudal region stout chevron bones are attached to the hypocentra, and inter- calated between these are two wedge-shaped pieces (Fig. 197). The interclavicle is rhomboidal, about half as long as the skull, and radially sculptured. Clavicles triangular, with short posterior pedicle ; coracoid and scapula ossified. Pore-limb less strongly developed than the hind, and with four digits. Ventral armouring of small, overlapping, transversely elongated scales, keeled, and pointed at one end (Pig. 193, E). In H. von Meyer's elaborate Monograph, published in 1858, no less than 271 ORDER I STEGOCEPHALIA 129 examples from the Lower Permian of Lebach, near Saarbriicken, are described, of which 102 are figured. The remains, lacking usually the tail, occur here in siderite nodules. A. decheni, v. Meyer. Sparagmites, Fritsch ; Discosaurus, Credner (Fig. 193, G). Lower Permian; Saxony and Bohemia. Chelidosa urus, Fritsch. Like Archegosaurus, but with broader and shorter skull, and no lachrymals. Lower Permian ; Bohemia. C. vranyi, Fritsch. Adinodon, Gaudry (Fig. 218). Basiocciput ossified. Vomers each with one large Imx IPor Fig. 216. Archegosav/rus decheni, v. Meyer. Lower Permian ; Lebach, near Saarbriicken. Young individual with traces of gill arches. 1/1 (after H. v. Meyer). Archegosaurus decheni, v. Meyer. Skull of adult individual, V-2- Per- mian ; Lebach, near Saarbriicken. Pm.r, Premaxilla ; Mx, Maxilla; La, Lachrymal ; Prf, Prefrontal ; J'tf, Postfrontal ; Por, Postorbital ; St, SO, Supratemporals ; Sq, Squamosal ; Pa, Parietal; QuJ, Quadrato-jugal ; Ep, "Epiotic" (^Supratemporal). tooth and numerous rugosities. Vertebrae rhachitomous. Lower Permian of Autun, France, and Bhenish Prussia. Gaudrya, Cochleosaurus, Fritsch. Lower Permian ; Niirschan, Bohemia. Euchirosaurus, Gaudry. Permian ; France. Sclerocephalus, Goldfuss (Onchiodon, Gein. ; Weissia, Branco). Over 1 m. VOL. II K 130 AMPHIBIA CLASS II long. Skull rounded anteriorly, orbits in hinder third, anterior nares far forwards, external bones coarsely sculptured. Pala- tines with minute teeth, maxillae and premaxillae with a series of large, conical, vertically grooved teeth. Dentine deeply folded. Vertebrae rhachi- tomous. Coracoid ex- panded, with concave pos- terior border; scapula long, slender, tapering. Ventral scales oat-shaped. Lower Permian ; Rhenish Prussia and Saxony. Melosaurus, Chalco- saurus, v. Meyer ; Zygo- saurus, Eichwald ; Platyops, Trautschold. Permian; Russia. Dendrerpeton, Owen. Coal Measures; Nova Scotia and Bohemia. Trimerorhachis, Zatra- FlG. 218. Aetinodon frossardi, Gaudry. Permian ; Muse, near Autun, France Palatal aspect of skull, with lower jaws. 2/ 5 (after Gaudry). Fm 219. Eryops megacephalus, Cope. Permian ; Texas. .1. Lateral aspect of skull. i/ 5 . B, Portion of the vertebral column. C, Caudal vertebrae. ' / 4 (after Cope). ORDER I STEGOCEPHALIA 131 chis, Dissorophus, Acheloma, Auisodexis, Cope. Permian; Texas and New Mexico. Eryops, Cope (Bhachitomus, Epicordylus, Parioxys, Cope), (Fig. 219). Largest of North American Stegocephalians. Skull 40-60 cm. long, and 30-46 cm. wide at occiput, elongated triangular, with somewhat tapering snout. Orbits round, relatively small, placed in hinder half of the skull. Anterior nares large, widely separated. Cranial bones rugose, sutures indistinct. Para- sphenoid very thick, dagger-shaped. On the palatine two large conical teeth. Maxilla and premaxilla with teeth of various sizes. Teeth sharply conical, on the top smooth, at the base ribbed. Vertebrae rhachitomous. Caudal vertebrae few in number, the posterior ones fused into a triangular piece, tapering acutely behind. Ribs strong, those of the sacrum very broad and short. Permian ; Texas and New Mexico. Cricotus, Cope. Total length, 3 m. General form elongate, with triangular skull and short, stout limbs. Snout narrow, orbits large, elongated oval, orbits situated near the middle of the skull. External bones faintly sculptured, sensory canals conspicuous, parietal foramen large. Teeth conical, of unequal si-ze. Presacral vertebrae composed of horseshoe - shaped pleurocentra and hypocentra, the former alone supporting the neural arch. In the caudals the pleurocentra and hypocentra form complete rings, and both elements take part in support of the neural arch, but the haemal arch is borne exclusively by hypocentra. and Illinois. C. heteroclitus, Cope. Diplovertebron, Fritsch (Fig. 198). Imperfectly known. Lower Permian; Bohemia. Brachyops, Owen ; Gondivanosaurus, Lyddeker. Trias (G-ondwana Beds) ; East India. Bothriceps, Huxley. Skull triangular, with very large parietals, and coarsely sculptured plates. Anterior nares far forwards. Teeth acutely conical, vertically grooved. Trias ; Australia and South Africa. H... --20. Micropholis granulata, Owen sp. Trias; Table Mountain, South Africa. A, Skull, from above. B, From the side -M/i (after Owen). Permian ; Texas Sub-Order D. STEREOSPONDYLI. Zittel. Vertebrae completely ossified, slightly amphicoelous, sometimes centrally perforated fur passage of the notochord. Basioccipital region ossified : sensory canals forming a lyra between the orbits and anterior it" res. Teeth with complicated infolding of the dentine. Family 1. G-astrolepidotidae. Zittel. Ventral armour consisting of elongated bony scutes. Radial prolongations of pulp rarity only moderately branched. Carboniferous and Permian. 132 AMPHIBIA CLASS II Anthracosaurus, Huxley. Skull broadly triangular, 36 cm. long, externally pitted. Orbits very small, situated in hinder third of the skull. Teeth externally furrowed, of nearly uniform size. Vomer toothless, palatines with a large tooth, and several of smaller size. Dermal scales externally con- vex, sharpened at the ends. Coal Measures ; Northumberland. A. russelli, Huxley. Loxomma, Huxley (Figs. 199, 221). Like the preceding, but orbits very large, irregu- larly oval, and teeth of unequal size. Coal Measures ; Northumberland and Bohemia. Eosaurus, Marsh. Known only by a few detached amphicoelous vertebrae. Coal Cross-section of tooth of Loxomma allmani, -»«- -v T a ,• Huxley, near the base. Enlarged. Coal Measures \ JN OVa bcotia. Macromerion, Fritsch. Imperfectly known. Permian ; Bohemia. Fig. 221. and Abbey). fringed enlarged Family 2. Labyrinthodontidae. (Eiujlypta, Miall.) Ventral armouring and sclerotic ring absent. Pectoral plates large, coarsely sculptured. Infolding s of the dentine completely labyrintliodont. A few excessively developed teeth present on the palatines, and sometimes on the vomer and symphysis of lower jaw. Trias. Trematosaurus, Braun (Fig. 222). Skull elongated triangular, about 25 cm. long, with orbits near the middle. Teeth present on jaw-bones, palatines, and vomer, and inner border of posterior nares with small denticles. A pair of greatly teeth present on symphysis of lower jaw, and behind these a supplementary row of small teeth. Two large vomerine tusks in advance of the posterior nares, and three or four palatine ones behind the same. Interclavicle rhomboid, with posterior pedicle. Abundant in the Bunt- sandstein of Bernburg. T. brauni, Burm. Metopias, v. Meyer (Metoposaurus, Lydekker), (Fig. 223). Skull large, broadly triangular, with elliptical orbits in anterior half, and large narial openings Nasals shorter than frontals and parietals. Pectoral plates very large. Ribs very powerful, distally expanded. Dentition weak, teeth strongly fluted externally, especially at the base, with but slight internal foldings. Teeth apparently arranged like those of Capitosaurus. Keuper ; Wurtemberg. (Figs. 224, 227). Skull Orbits small, behind the frontals or larger. A small auditory notch adjacent One or two powerful tusks present on vomer in Fig. 222. Skull of Trematosaurus brauni, Bur nieist. Buntsandstein !/ 4 (after Burmeister). Bernburg. with muzzle often broad middle of skull. Nasals Capitosaurus, Munst. and obtusely rounded, of equal size with the to the so-called epiotic. front of the internal nares and on palatines behind the same. Between the ORDER I STEGOCEPHALIA 133 vomer and premaxillae is an aperture to give play to the two median tusks of the lower jaw. Keuper ; Wurtemberg, Franconia, Silesia. Fig. 223. Cwpitosawus nasutus, v. Meyer. Buntsandstein ; Bernlmrg. Dorsal aspect of skull. QuJ Fig. 224. Metopias d iagnosticus, v. Meyer. Ven- t ral aspect of skeletal fragment. Keuper ; Hahnweiler, near Stuttgart. i/s (after E. Fraas). Fig. 225. Cyclotosavjms rdbustris, v. Meyer. Keuper; Feurerbach, near Stuttgart. Palatal aspect of skull. Cyclotosaurus, Fraas (Fig. 225). Similar to Cajntosaurus, except that the auditory notch is closed behind by the union of the external supratempora with the prosquamosal. Keuper ; Wiirtemberg. 134 AMPHIBIA CLASS II Mastodonsaurus, Jaeger (Figs. 204, 206, 226). Largest of all Labyrintho- donts, skull T25 m. long, depressed, and with large orbits behind the middle. External bones sculptured, sensory canals prominent. Premaxillae pierced for the passage of the two greatly enlarged teeth at symphysis of lower jaw. Vomers with a pair of tusks in front of the posterior nares, and another near the hinder margin ; palatines with a single series of large teeth. Dentine excessively complicated. Interclavicle rhomboidal, clavicles triangular, all strongly sculptured. Ischium very large, pubis small, ilium elongated, and articulating with the sacral ribs. Limbs very imperfectly known, and dermal armour not observed. The most perfect re- mains are from the Lettenkohle of ang Skull of Mastodonsaurus giganteus, Jaeger. A, Orbit ; N, External nares ; X, Openings for the passage of the tusks of lower jaw ; Pmx, Pre- maxilla ; Mx, Maxilla ; Na, Nasal ; La, Lachrymal ; Pfr, Prefrontal ; Fr, Frontal ; Ptf, Postfrontal ; Pa, Parietal ; PtO, Postorbital ; Sq, Squamosal ; SO, Supratemporal ; Ep, Epiotic ; J, Jugal ; Qj, Quadrato-jugal ; ExO, Exoccipital (after E. Fraas). Fig. 227. Lower jaw of Capito- saurus nasulus, v. Meyer. Trias Bern- burg^ Fig. 22S. Footprints of Cheirotheriwm barthi, Kaup. Buntsandstein; Hessberg, near Hildberghausen. 1/6 (after Owen). Gaildorf and Oedendorf in Wiirtemberg. Fragments occur also in the Upper Trias of England and India, and possibly also in the Buntsandstein of Alsace and the Black Forest. Labyrinthodon, Owen. Upper Trias ; England. fihyfidosteus, Owen. Karoo Formation ; Orange Free State. Pachygonia, Gonioglyptiis, Huxley. Trias ; East India. Footprints. — Stegocephalian footmarks are not uncommon in the Coal order in URODELA 135 Measures of Nova Scotia, Pennsylvania, Kansas, and elsewhere. They occur also in the Rothliegendes of Thuringia, Saxony, and Bohemia ; in the Karoo Formation of South Africa, and the Connecticut Valley Trias. More notable still are the Buntsandstein localities in Thuringia (Fig. 228) and Franconia, and those of the English and Franconian Keuper. The impressions always occur along stratification planes, and on removal of the superjacent layer the counterpart appears in relief, and is usually accompanied by a series of fossil mud-cracks. Most of these tracks are five-toed, although some occur in which the manus, which is invariably of smaller size than the pes, has but four digits. Order 2. GYMNOPHIONA. (Apoda, Oppel.) Vermiform amphibia core red with small scales, arranged in transverse rings, and without limbs. Vertebrae amphicoelous, with persistent notochord. Cranium ossified ; maxillae and palatines with small, backwardly curved teeth. Bibs weakly developed. Pectoral and pelvic arches absent. The Coecilians constitute a small group restricted to the South American and Indo-African tropics, and are unknown in the fossil state. Order 3. URODELA. 1 (Caudata ; Batrachia gradientia.) Elongate amphibia with naked skin, usually with two pairs of short limbs and perennial tail, loith or without external gills. Cranium without supraoccipital, post- orbitals, and supratemporals. Vertebrae usually completely ossified. No parietal foramen. Bio-sacral connection acetabular. Urodeles are distinguished from Stegocephalians chiefly by their naked body, solid vertebrae, extremely short ribs, and peculiarities in the conforma- tion of the skull and pectoral arch. The vertebrae may be either amphicoelous or opisthocoelous, are rarely pierced for the notochord, and have weakly developed spinous and transverse processes. The skull, which is broad, flattened, and anteriorly rounded, remains partly cartilaginous even in the adult, and both membrane and cartilage bones are among its components. The cranial roof is formed by the parietal, frontal, and prefrontal elements, adjoining which on either side are the large temporal fossae and orbits. The nasal capsule is sometimes covered by ossified nasals, and sometimes remains cartilaginous. The anterior and lateral margins of the skull are formed by the premaxillae and maxillae, but the latter are sometimes entirely wanting. In the basioccipital region only the exoccipitals are ossified, and the auditory capsule remains either cartilaginous or partially ossified, being covered by a thin, transversely elongated squamosal. Jugal and quadrato-jugal are absent, the quadrate is small, and only its articular extremity is ossified. Parasphenoid, vomers, and pterygoids are conspicuous on the under side of the skull, but the palatines are frequently atrophied. 1 Meyer, H. con, Zur Fauna ju, Quadrate; QVJt Quadrato -jugal ; S, Supratemporal vacuity; so Supraoccipital ; sq, Squamosal ; vo, Vomer.) ORDER I RHYXCHOCEPHALIA 147 Sub-Order 1. PROTEROSAUEIA. Seeley. (Proganosauria, Baur.) Abdominal ribs small, arranged in several longitudinal series. Pubis and ischium imperfectly fused. Fifth metatarsal not dissimilar from the rest. Marginal teeth in a single uniform series. The sub-order is of interest as comprising some of the most primitive and most ancient reptiles known to science. They are regarded by many authors as ancestral not only to the Sphenodon group, but to all Archosauria, or reptiles with two cranial arches. There is much reason to suppose that from these forms also a Dinosaur-avian stem was evolved in the Permian, from which birds have come down to us. Family 1. Proterosauridae. Maxillae, premaxillae, and mandibles with a series of large conical teeth, either acrodont or implanted in shallow alveoli, and smaller teeth present on the palatines and vomer. Interclavicle elongate, with a rhombic expansion at its anterior end. Permian and Trias. Palaeohatteria, Credner (Fig. 238). Body lizard-like, about 25 cm. long. Vertebral centra in the form of delicate constricted amphicoelous cylinders, lin.l M D E Fig. 238. Palaeohatteria longicaudata, Credner. Lower Permian: Saxony. A, Skull, somewhat distorted, l /i- 5, Pectoral arch. ' C, Pelvic arch. D, Dorsal vertebra; E. Caudal vertebra, anterior aspect. (". Acetabulum; d, Clavicle ; cor, Coracoid ; f, Femur; ft., Humerus ; ic, Intercentrum ; interclavicle; il, Ilium; ju, Jugal; la, Lachrymal; n, Pedicle of neural arch; na, Nasal; o, Obturator notch ; pmx, Premaxilla; por, Postorbital ; prf, Prefrontal; pu, Pubis; quj, Squamosal and quadrate; vo, Vomer (dis- placed); :. Zyapophysis. Orbit overlaid by displaced facial bones of the right side), (after Credner). with persistent notochord ; small intercentra occur between all in advance of 148 REPTILIA class m about the sixth caudal, and single-headed ribs borne by all the vertebrae as far as the seventh caudal. Abdominal ribs represented by numerous small oat-shaped scutes. Premaxillae small, with three or four recurved teeth. Inferior border of orbit formed by jugal alone. Digits clawed. Habits probably aquatic, as indicated by the comparatively unossified extremities of limb bones. Lower Permian (Rothliegendes) ; Niederbasslich, near Bonn. Kaclaliosaurus, Credner. A land form accompanying the preceding ; limb bones completely ossified proximally and clistally, with spongy interior. Extremities much longer than in Palaeohatteria ; humerus and femur of equal length, but metacarpals shorter than metatarsals. Proterosaurus, v. Meyer. Attaining a length of 1/5 m. Vertebral centra completely ossified, and united with their neural arches by suture. Inter- centra occur only between the cervical vertebrae, which are elongate, and bear slender ribs. Skull tapering anteriorly, its structure not clearly shown. Hind limb considerably longer than the fore, and distal tarsals less than five in number. Upper Permian (Kupferschiefer) of Thuringia and Hesse, and Magnesian Limestone of Durham, England. P. speneri, v. Meyer ; P. UncJci, Seeley. Aphelosaurus, Gervais ; Haptodus, Gaudry. Lower Permian ; Autun and Lodeve, France. Telerpeton, Mantell. Supposed Trias of Elgin, Scotland. Sub-Order 2. PELYCOSAUEIA. Cope. 1 Anterior teeth enlarged, incisor- and canine -like, the remainder conical and molariform ; none of the teeth with lateral cusps, but sometimes serrated. Neural spines enormously developed in some genera. Sacrum of three vertebrae. Limbs very short and strong. Family 1. Clepsydropidae. Cope. Skull long and narrow, truncated posteriorly . External nares separated, terminal, t opening directly into the mouth. Orbits large, round, placed behind the middle of the si- nil ; supratemporal vacuity small. Quadrate small, nearly enclosed by surrounding bones. Anterior incisors and canines of upper jaw much larger than other teeth. Numerous small conical teeth present on palatines, pterygoids, and vomer. Proximal tarsals two in number. Permian. Clepsydrops, Cope. Neural spines of the lumbar and sacral regions greatly elevated. Intercentra present between the dorsal and caudal vertebrae ; anterior ribs double-headed, posterior single-headed. Teeth large, with sharp cutting edges. Permian ; Texas, Illinois, and Kansas. Dimetrodon, Cope. Larger than the preceding, skull upwards of 0"5 m. long, and with similar dentition. Intercentra present between the dorsals ; all the ribs double-headed from the axis on. Neural spines rising from the axis until in the dorsal region they are many times longer than the diameters of the centra. Permian ; Texas. 1 Literature : Baur, G., and Case, E. C, On the morphology of the skull of the Pelycosauria and the origin of the Mammals (Anat. Anz. vol. XIII. p. 109), 1897. — The history of the Pelycosauria, with a description of the genus Dimetrodon (Trans. Amer. Phil. Soc. vol. XX. pt. 1), 1899.— Case, E. C, The Vertebrates from the Permian Bonebed of Illinois (Journ. Geol. vol. VIII. p. 698), 1900. ORDER I BHYXCHOCEPHALIA 149 Naosaurus, Cope (Fig. 239). Differs from the last in that the neural spines bear transverse processes. Per- mian ; Texas and Bohemia. Embolophorus, Theropleura, Archaeo- bolus, Lysoropjhus, Cope. Permian ; Texas. Stereorachis, Gaudry ; Calli- brachion, Boule and Glengeaud. Per- mian ; Autun, France. Known by im- perfect remains apparently allied to Dimefrodoii. Sub-Order 3. RHYNCHOCEPHALIA VERA. Abdominal ribs reduced to three relatively large longitudinal series ; pubis and ischium well ossified; fifth metatarsal very much shortened, and somewhat expanded. Mar- ginal teeth in one or more uniform series. . Fin. 24 J. Hyperodapedon gordoni, Huxley. Upper Trias; Elgin, Scotland. A, Superior aspect of skull, ' ; . B, Palate. C, Mandibular symphysis from below. ". Orbit; md, .Mandibular fork; mx, Maxilla; //. Nasal ; }J, Palatine ; pmx, Premaxilla ; s, Supra Fig. 239. Naosaurus claviger, Cope. Permian; Texas. Dorsal vertebrae, anterior and lateral aspects, J 4 (after Cope). Family 1. Rhynchosauridae. Skull short and broad, with a beak-like rostrum formed in/ the downwardly curved, slender, toothless premaxillae. Mandibles with a single, and maxillae and palatines with several longitudinal series of depressed temporal vacuity; s', Lateral temporal vacuity), COnicdl teeth. External /tares COnfhlmf. (after Huxley). •> Trias. Hyperodapedon, Huxley (Fig. 240). Body stout, upwards of 2 m. long. 150 EEPTILIA class in Mandibular rami fused in a long symphysis, which is slightly forked at its toothless anterior end ; posteriorly with a single series of obtuse teeth. Parietal foramen and intercentra apparently wanting. Cervical vertebrae opisthocoelous ; limbs imperfectly known. Supposed Trias of Elgin, Scotland, and Central India. lihynchosaurus, Huxley. Smaller, and with fewer teeth than the preceding ; mandible toothless or with minute teeth, maxillae with a single row, and palatines with a double row of small teeth. Vertebrae amphicoelous ; ab- dominal ribs well developed. Upper Trias ; Shropshire and Warwickshire. Family 2. Mesosauridae. 1 Small lacertiform reptilia, with very numerous, extremely long and acicular teeth in the upper and lower jaws. Vertebral centra amphicoelous, with remnants of the notochord. Cervical vertebrae vnth short hatchet -shaped ribs. Dorsal ribs single -headed, very thick. Ventral ribs well developed. Tarsus with two rows of small bones. Extremities with five toes. Mesosaurus, Gervais (Dilrochosaurus, Gurich). Karoo formation of South Africa. Stereosternum, Cope, from the Permian or Lower Trias of Brazil is possibly identical with, in any case very similar to Mesosaurus. Family 3. Champsosauridae. Skull with elongated gavial-like snout. A single series of large conical teeth present on the jaw-bones and palatines, and irregular longitudinal series of minute teeth on the vomers, palatines, and pterygoids. External nares terminal and confluent. Mandibular rami suturally united at the symphysis. Only two intercentra present at anterior end of the neck. Vertebral centra completely ossified, slightly biconcave, or amphiplatyan, and suturally united with their neural arches. Cretaceous and Lower Eocene. Champsosaurus, Cope {Simaedosaurus, Gervais). Large aquatic reptiles attaining a length of 2*5 m. Premaxillae elongated into a gavial-like rostrum ; cervical ribs short and double-headed ; abdominal ribs stout. Humerus with ectepicondylar groove instead of foramen. Known by fragmentary remains from the Laramie Cretaceous, and Lower Eocene of the United States, and by complete skeletons from the Lower Eocene of France and Belgium. Family 4. Sauranodontidae. Small long-tailed Rhynchocephalia with edentulous jaws and beak-like rostrum. Temporal fossae small, parietal foramen wanting, postorbita I very large, external nares undivided. Vertebrae well ossified ; second sacral rib distally divided ; abdominal ribs stout. Fore-limb shorter than the hind, both pentadactylatc. Dermal scales rectangular. Upper Jura. Sauranodon, Jourdan. This, the solitary genus, is known by perfect skeletons from the Upper Jura of Cerin, France. S. incisivus, Jourdan, attains a length of about 0*7 m. 1 Geinitz, H. B., Sur Stereosternum tumidum, Cope (Ann. Soc. Geol. Belg. vol. XXV. bis p. 35), 1900. — Woodward, A. S., On a new specimen of Stereosternum (Geol. Mag. [4], vol. IV. p. 145), 1897. ORDER I RHYNCHOCEPHALIA 151 Family 5. Sphenodontidae. Vertebrae amphicoelous, sometimes with persistent noto- chord ; intercentra present in cervical and caudal regions. Premaxillae each with a small pointed tooth. A single series of depressed, triangular, acrodont teeth present on maxillae, mandibles, and outer edge of the palatines ; vomer toothless. External nares separated ; interclavicle T-shaped; dermal scales subrectangular. Upper Jura to Recent. Homaeosaurus, v. Meyer (Sapheosaurus, v. Meyer), (Fig. 241). Attaining a length of between 20 and 40 cm., and differing from the recent Sphenodon in that intercentra are absent between the dorsal vertebrae ribs without uncinate processes, and humerus not pierced by entepicondylar foramen. Mandibular rami united at the symphysis by ligaments ; second sacral rib bifid distally. Upper Jura (Lithographic Stone) ; Bavaria, and Cerin, France. Kimmeridgian of Hanover, and Purbeckian of England. H. maximiliani, v. Meyer. Ardeosaurus, Acrosaurus, v. Meyer ; Euposaurus, Jourdan. Upper Jura (Lithographic Stone) ; Bavaria, and Cerin, France. Pleurosaurus, v. Meyer (Anguisaurus, Miinst. ; Sauro- phidium, Jourdan). Body serpentiform, upwards of 1*5 m. long, the tail forming one-third the total length. Snout tapering in front. Presacral vertebrae with stout single-headed ribs ; abdominal ribs well developed. Fore-limbs shorter than the hinder pair. Upper Jura (Lithographic Stone) ; Bavaria, and Cerin, France. P. muensteri, Wagner. Sphenodon, Gray (Hatteria, Gray). Inferior border of the large orbits formed by maxilla external nares divided ; a single tooth on either Fig. '241. Homa&osaurus pulchellus Zittel. Upper Jura ; Kel- heim, Bavaria. Ventral aspect, Vo. side of the premaxillary beak ; intercentra present between all the vertebrae, humerus with both entepicondylar and ectepicondylar foramina or grooves. Recent, inhabiting certain islands off New Zealand. VERTICAL RANGE OF THE RHYNCHOCEPHALIA. Divisions. Permian. Trias. Jura. s CD S ® o o £ Z o c - Recent. I. PllOTEROSAURIA .... II. Pelycosauria .... III. Rhyxchocefhama Vera. 1. Rhynchosauridae . 2. Mcsosauridae .... ■i. Champsusauridae . 4. Sauranodontidae 5. Sphenodontidae _ ' 152 REPTILIA class hi Order 2. SQUAMATA. (Lepidosauria, Streptostylica.) 1 Body elongate, covered with corneous, or more rarely -with dermal sccdes or scutes. Quadrate movably attached to the skull; the lower temporal arcade always, and upper temporal arcade frequently wanting. Palatcd vacuities large, pterygoids not in contact with vomer ; external nares separated ; teeth acroclont or pleurodont. Vertebrae well ossified, usually procoelous, rarely amphicoelous ; sacral vertebrae not more than tvjo in number. Post-cervical intercentra and abdominal ribs wanting ; dorsal ribs single- headed. Limbs adapted for ambulation or natation, absent only among Ophidia and a few Lacerfilia. This order comprises Lizards, Snakes, and two extinct groups of aquatic reptiles, — Dolichosauria and Pythonomorpha, — the earliest clearly recognised members of which occur in the Cretaceous. The Squamata are evidently very closely allied to Rhynchocephalians, and in all probability their origin is to be traced to that group. » Sub-Order 1. DOLICHOSAURIA. Small, aquatic, serpentiform reptiles, with well-developed lizard-like limbs and limb- girdles. Vertebrae procoelous, and articulated both by zygapophyses and zygosphene- zygantrum arrangement. Sacral vertebrae not anchylosed. Mandibles with sutural symphysis. Teeth pleurodont. The family Dolichosauridae comprises a few genera from the English Chalk and the Upper Cretaceous of Istria and Dalmatia, the largest of which^ attain a length of between two and three metres. Dolichosaurus, Owen, has no less than seventeen cervical vertebrae and large hollow ribs. Acteosaurus, Adrio- saurus, Aigialosaurus, Ca.rsosaurus, Pontosaurus, and Mesoleptos are allied Istrian genera. Most of the detached vertebrae of Cretaceous age, commonly classed as Ophidian, are doubtless Dolichosaurian. Like the Pythonomorphs, these forms probably passed away without leaving any post-Cretaceous descendants. Sub-Order 2. PYTHONOMORPHA. Cope.- Large marine reptiles with elongate body and two pairs of paddle-shaped appen- dages. Skull lizard-like, elongate, depressed; superior temporal arcade and pineal 1 Cope, E. D., Crocodiles, Lizards, and Snakes of North America (Ann. Rept. Smithsonian Inst., 1898), 1900. 2 Literature : Baur, G., Morphology of the skull of the Mosasauridae (Journ. Morphol. vol. XII., No. 1), 1892. — Cope, E. D., The Reptilian orders of Pythonomorpha and Streptosauria (Proc. Boston Soc. Nat. Hist. vol. XII. p. 250), 1869. — The Vertebrata of the Cretaceous Formations of the West (Rept. U.S. Geol. Surv. Territ. vol. II.), 1875.— Professor Owen on Pythonomorpha (Bull. U.S. Geol. Surv. Territ. vol. IV. p. 299), 1878. — Cuvier, G., Sur le grand animal fossil de la craie de Maestricht (Ann. Mus. d'Hist. Nat. vol. XII.), 1808. — DoIIo, L., Note sur l'osteologie des Mosasauridae (Bull. Mus. Roy. d'Hist. Nat. Belg. vol. I.), 1882.— Ibid, vol. IV., 1885.— Nouvelle Note, etc. (Bull. Soc. Belg. de Geol. Pal. et Hydrol. vols. III. -VII.), 1889-94.-6'^^, R. W., A Memoir on Mosasaurus, etc. (Smithson. Contr. Knowl. vol. II.), 1864. — Goldfuss, A., Der Schadelbau des Mosasaurus (Nova Acta Acad. Caes. Leop. Car. nat. cur. vol. XXL), 1843. — Leidy, J., Cretaceous Reptiles of the United States (Smithson. Contrib. Knowl.), 1864. — Extinct Vertebrate Fauna of the Western Terri- tories (Rept. U.S. Geol. Surv. Territ. vol. I.), 1873.— Marsh, 0. C, Characters of Mosasauroid Reptiles (Amer. Journ. Sci. [3], vol. I.), 1871.— Ibid. vol. III. (1872) ; and XIX. (1880).— Merriam, J. C, Die Pythonomorpha der Kansas Kreide (Palaeontogr. vol. XLL), 1894. — Osborn, H. F., A complete Mosasaur Skeleton (Mem. Amer. Mus. Nat. Hist. vol. I. pt. 4), 1899. — Owen, R., On the ORDER II SQUAMATA 153 foramen present ; premaxillae and nasals fused into a simple rostrum; quadrate large, perforate, and movably attached to squamosal and prosquamosal ; parietal un- paired and joined to the supraoccipitals and probtics by decurved lateral processes. Mandibular rami united at the symphysis by ligament, and with a movable articulation behind the middle of each ramus. Teeth large and conical, fixed by tumid bases in shallow alveoli of the jaw-bones and pterygoids. Sclerotic ring present. Vertebrae procoelous, cervicals tvith hypapophyses. Sacrum wanting; sternum probably never ossified ; interclavicle (episternum) sometimes present, but no clavicular arch. Limb- bones short, but the digits are lengthened by an increased number of phalanges, the ungual ones clawless. The vertebral column comprises 115-130 or perhaps more procoelous vertebrae, and is sometimes divisible into cervical, dorsal, lumbar, and caudal regions. The distinction between dorsal and lumbar series is not very decided, however, except that the latter bear shorter ribs. The transverse processes are short and thick in the precaudal vertebrae for the attachment of single- headed ribs; in the caudals they are flattened and elongated but not costiferous, and become obsolete at about the middle of the tail. The neural arches are always, even in young individuals, thoroughly coossified with their centra; the neural spines are of moderate length, but sometimes notably elongated in the posterior region of the tail. The zygapophyses are strong in the cervical and anterior thoracic region, but become weaker and finally disappear in the tail. Y-shaped haemapophyses or chevron bones are present in all the caudals with the exception of the first five or more, to which the name " pygals " has been given ; each chevron articulates vith its own centrum. The only with its own centrum. The atlas is composed of a wedge- shaped intercentrum below, and two lateral pieces or neuropo- physes, as in lizards, its centrum being represented by the odontoid process of the axis. A wedge- shaped intercentrum occurs be- tween the atlantal intercentrum and the axis. The axis and five following cervicals bear each a more or less stout exogenous hypapophysial process, to the ex- tremity of which is attached a small, free epiphysis, correspond- ing morphologically to an inter- centrum (Fig. 242). This is wanting in the last cervical, and the process itself is rudimentary. The skull (Figs. 243, 244) resembles that of Varanus more F z- FlG. 242. Clidastes stenops, Cope. Upper Cretaceous ; Kansas. An- terior cervical vertebrae .-I, From the side. /;, From in front, !/ 2 . (c, Centrum ; d. Transverse process; h, Hypapo- physial epiphysis or intercentrum; hy, Hypapophysis ; jn:. Prezygapophysis ; sp, Neural spine), (after Cope). nearly than that of other living reptiles. The parietals, frontals, and pre- rank and affinities of the Mosasauridae (Quar. Journ. Geol. Soc. vol. XXXIII. p. 682), 1877.— Ibid vol. XXXIV. (1878), p. n8.— Williston, S. W., On Mosasaurs, etc. (Kansas Univ. Quar. vol. ii. p. 83), 1893. — Ibid. vol. III. (1895), p. 165.— University Geol. Surv. Kansas, vol. IV. Topeka, 1898. — Williston, S. W., and Case, E. <'.. Kansas Mosasaurs (Kansas Univ. Quar. vol. I. p. 1), 1892. 154 REPTILIA CLASS III maxillae are all unpaired, as are also the nasals, which are fused with the premaxillae. The supratemporal vacuity is bounded externally by the prosquamosal and postorbital, which form a narrow arcade. The squamosal is intercalated between the exocciptal ( = parocciptal, Baur) and the prosquamosal, and sends a slender process inwards between the exoccipital and prootic, extending nearly as far as the brain cavity. The suture between the postorbital and postfrontal is often obliterated. Super- ciliary plates have not been observed, and are often functionally replaced by the horizontally expanded prefrontals. The jugal unites with a descending process of the postfrontal, and these two bones together with the prefrontal com- pletely enclose the orbit. There is a complete Bo Opo Fig. 243. Clidastes propython, Cope. Upper Cretaceous; Kansas. Palatal aspect of skull,! partly restored, (bo, Basi- occipital ; mx, Maxilla; )>l, Palatine; /mix, Premaxilla ; pt, Pterygoid ; ptf, Postorbito- frontal ; opo, Supratem- poral ; ipij, Squamosal ; sph, Basi- spheuoid ; vo, Vomer.) Fio. 244. Platecarpus coryphaeus, Cope. Upper Cretaceous; Kansas. Pos- terior aspect of skull, 1/4. (bo, Basioccipital ; eo, Exoccipital ; p, Parietal; pe, Prootic; pfo, Postorbito - frontal ; pt, Pterygoid; 7, Quadrate; so, Supraoccipital ; sij, Squamosal; st, Stapes), (after Williston.) parietal arch formed by a slender process of the parietal uniting with a process of the squamosal. The quadrate (Figs. 245, 246) is relatively large, and movably articulated with the squamosal and prosquamosal. Its antero-superior margin is dilated into a broad thin plate, and its posterior margin is notched or perforated for the auditory meatus. This opening is either partially or completely enclosed posteriorly by the stout suprastapedial process, which is especially character- istic of the Mosasaur quadrate. On the concave inner side of the quadrate, near the upper part of the meatal notch, is a small pit for the lodgment of the outer end of the stapes. The quadrate exhibits wide variation in form and size amongst the different genera. The transverse bone, or ectopterygoid, is always small, and joins the pterygoid and jugal only. A slender columella, or epipterygoid, is present in all cases. The mandibular rami were united at the symphysis by ligaments. Somewhat back of the middle of each ramus, between the angular and splenial, and the dentary and surangular, there is a movable articulation permitting of a wide distension of the jaws. ORDER II SQUAMATA 155 A single series of large conical teeth occurs in both upper and lower jaws, those of the pterygoid being inferior to the rest in size. The crown often exhibits slight anterior and posterior carinae, and may be bevelled into several longitudinal facettes ; and the enamelled surface may be either smooth or /; Fig. 245. Mosasaurus camperi, v. Meyer. .4, Outer; and B, Inner aspect. V4. (al, Suprastapedial process ; k, Stapedial pit; I, Meatus ; m, Superior margin ; n, Inferior margin), (after ( >wen.) Clidastes propython, Cope. Quadrate, inner aspect, - :; . (Lettering as in l-'ig. 245), (after Cope). delicately striated. All the teeth are fixed by tumid osseous bases in shallow pits of the supporting bone. Successional teeth arise alongside the functional ones, and gradually displace them by pressure against the crown on the inner side. The pectoral arch (Fig. 247) exhibits a rather ;large and flattened coracoid, the articular border of which is thickened and divided into two facettes Flo. 247. clidastes velox, Marsh. Pectoral arcli, dorsal aspect, i/ 5 . fa Coracoid ; h, Humerus : mc, Metacarpus ; r, Radius ; sc, Scapula; it, Ulna ; I-V, Digits), (after Marsh). meeting at an obtuse angle, while the thin inner edge is rounded, and often incised by a deep notch or emargination. There is a small coracoid foramen situated toward the articular border. Posteriorly the coracoids meet the sternum, which was probably never ossified, but composed of calcified cartilage, quite like the sternal ribs. The coracoids are separated from each other by a broad epicoracoidal expanse of cartilage. The scapula is placed as in Rhyn- chocephalians ; a slender interclavicle (episternum) is present, but clavicles are 156 EEPTILIA CLASS III wanting. The humerus is short and stout, its articular ends expanded, and the distal end with two facettes for the bones of the second segment. Of the latter the radius is distally expanded. The carpals vary in number from seven (arranged in two rows) in Clidastes and Mosasaurus, to one or two rudimentary ossicles in Tylosaurus. There are five metacarpals, differing in shape amongst the various genera, and supporting a variable number of phalanges ; these last being comparatively few in Clidastes and Mosasaurus, and as many as eleven or twelve in the paddles of Tylosaurus. None of the digits are clawed. The pelvic arch (Fig. 248) is more weakly developed than the pectoral. The ilium is a slender rod-shaped bone, its superior end free or loosely attached to the single vertebra which functions as a sacrum. The pubes probably do not meet in a ventral symphysis, but the ischia are joined along ^>^f Fig. 24S. Platecarpus simus, iarsh sj>. Upper Cretaceous ; Kansas. Pelvic arch and paddles, !/i2- (/, Femur; /', Fibula; il, Ilium ; is, Ischium ; rut, Metatarsus; pb, Pubis; t, Tibia; I-V, Digits), (alter Marsh). an extensive articular surface. The bones of the hind limb resemble those of the fore, but are more slender, and somewhat smaller. There are probably never more than three tarsals, and sometimes only one. Four or five digits are developed, with a variable number of phalanges. As a rule the posterior paddles are smaller than the anterior pair. The limbs of Pythonomorphs and Cetaceans furnish an excellent illustra- tion of the influence of environment in producing analogous structures among widely divergent groups. As a result of their complete adaptation for an aquatic existence, Mosasaurs and whales have developed a very similar form of body. Most of the Pythonomorphs were of large size, and enjoyed a wide distribution, their remains being known from the Upper Cretaceous of Europe, North and South America, and New Zealand. The Pythonomorphs were covered externally with scales very similar in size and structure to those of Varanus. These scales have been found impressed upon the bones of the skull, indicating the absence of corneous plates. There were no dermal ossifications of any kind. Small or medium- sized fishes have been observed in the fossilised stomach contents in several instances. The earliest discovered cranium, found in the Maestricht Chalk in 1780, was mistaken for that of a Cetacean or Crocodilian until Cuvier demonstrated its remarkable similaritv to the skull of Varanus. Owen united Mosasaurs with lizards under the designation of Lacertilia natantia. The name Pythono- morpha was proposed in 1869 by Cope, who regarded the group as inter- mediate between snakes and lizards. It is argued by Dollo and Williston,. order ii SQUAMATA 157 however, that Pythonomorphs could not have been ancestral to the modern Squarnata, since it is impossible to suppose that forms which became so highly specialised and completely adapted to an aquatic existence, should have ever again reverted to a generalised condition, and reassumed terrestrial habits. Pythonomorphs arose undoubtedly from land animals, and may have sprung from Dolichosaurian ancestors ; but they appear to have passed completely out of existence near the end of the Cretaceous, without leaving any progeny. Their extreme differentiation is attested by the loss of a sacrum, multiplica- tion of phalanges, degeneration of the hind paddles, development of a man- dibular joint, and other characters, of which no heritage remains amongst modern Squarnata. Family 1. Mosasauridae. This family, with the characters of the sub-order, comprises three rather divergent groups, which are considered of sub-family value. Restricted to the Upper Cretaceous. Sub-Family A. Tylosaurinae. "Williston. Hind limb functionally pentadactyle. Trunk short, tail 'proportionately long. Premaxillae produced into a long rostrum in advance of the teeth ; quadrate with short suprastapedial process. Carpus and tarsus almost wholly unossified; phalanges numerous. Vertebrae without, or with very rudimentary zygosphenes. Tylosaurus, Marsh (Liodon, Cope ; Macrosaurus, Owen ; Rhinosaurus, Marsh). Skull - 7 to over 1 m. long. Superior surface of parietal smooth and produced to the posterior margin in the median line, with nearly parallel sides ; foramen at its anterior margin. Postfrontal and prefrontal meeting on the superior border of the orbit ; quadrate stout, with very short suprastapedial process ; maxilla with about thirteen large teeth. One or two carpal and tarsal bones present, not articulating with adjacent elements. Coracoid not emarginate ; limbs about equally developed ; phalanges numerous ; fifth digit elongate. Haemapophyses loosely articulated ; no zygosphenes. Niobrara Group ; Kansas, New Mexico, and Texas. T. proriger, T. dyspelor, Cope. Hainosaurus, Dollo. Skull upwards of 1*5 m. long. Frontal broad; pre- frontal and postfrontal meeting over the orbit ; teeth of unequal size. Carpals reduced in number ; phalanges fewer than in Tylosaurus, and paddles relatively larger. Haemapophyses loosely articulated ; cervicals with small zygosphenes. Upper Cretaceous ; Belgium. Sub-Family B. Platecarpijstae. Williston. Hind limb functionally pentadactyle. Trunk short, fail proportionately long. Premaxillae short, very obtuse, and projecting but little in front of the teeth. Quadrate large, with a long suprastapedial process. Carpus and tarsus imperfectly ossified. Vertebrae' with rudimentary (or functional?) zygosphenes. Interclavicle probably present in all forms. Platecarpus, Cope (Lestosaurus, Marsh; ? Holcodus, Gibbes), (Figs. 248-250). Total length about 5 m., of which the skull forms one-eighth. Superior sur- face of parietal small, triangular, not reaching beyond the middle of the bone ; large oval foramen at its anterior border. External nares much dilated 158 KEPTILIA CLASS III anteriorly. Quadrate large, with prominent supra- stapeclial process extending below the middle of the bone ; opening for the auditory meatus large, not entirely enclosed. Teeth slender and recurved, facetted on the outer side, striate on the inner ; maxillae with about twelve, and pterygoid ten to twelve teeth. Coracoid deeply emarginate on inner border. Four carpals and three tarsals present, closely articulating. Fifth digit shorter than the fourth, and divergent. Chevron bones large, loosely articulated. Abundant and represented by numerous c CD (V u o -4-< CO a; ^ Pi e O o S e i h m '<$> Fig. 249. Plateau-pus coryphaeus, Cope. Upper Cretaceous ; Logan County, Kansas. Skull, superior and lateral aspects, 1/7 (after Merriani). species in the Upper Cretaceous of Kansas, Colorado, Texas, North Dakota, and France. Holosaurus, Marsh. Yery similar to the preceding, except that the coracoids are not emarginate ; there are no zygosphenes in the only known specimen. Kansas. Plioplatecarpus, Dollo (Oterognathus, Dollo). Similar to Platecarpus, but with smaller chevron bones. Quad- rate with large meatal opening. Mandible slender, coronoid rudimentary. Teeth long and slender, facetted, and striate. Danian of Maestricht, and Upper Senonian of Belgium. Prognathosaurus, Dollo. Skull about 0*6 m. long. Pterygoids nearly as large as the maxillae, and with very powerful teeth. The large suprastapedial process of the quadrate coossifles with the infrastapedial process, and encloses an oval foramen. A wide canal ORDER II SQUAMATA 159 lower part of the basioccipital. Mandible strong, upper edge Coracoid non-emarginate ; chevrons present in concave, coronoid process prominent loosely articulated. Brown Phosphate Chalk ; Belgium. Brachysaurus, \Yilliston. Frontal large and broad; no median basioccipital canal. Suprastapedial process of quadrate coossified with the infrastapedial. No zygosphenes ; chevrons fused with their centra. Possibly identical with preceding genus. Ft. Pierre Cretaceous; South Dakota. Phosphor osaurus, Dollo. Imperfectly known. Frontal very narrow, with nearly parallel sides, and taking part in the superior border of the orbit. Parietal small ; its exposed surface triangular, and with very large foramen at its front margin. Suprastapedial process much elongated and united witli the infrastapedial, enclosing an elongated meatal opening. Tympanic cavity extended and shallow. Upper Cretaceous ; Belgium. Taniwhasaurus, Hector. Allied to Platecarpus. Cretaceous; New Zealand. Sub-Family C. Mosasaurixae. Williston. Hind limb tetradactyle. Trunk elongated, tail much dilated distally. Pre- maxillae forming a short and obtusely conical rostrum. Prefrontals more or less dilated into a horizontal plate posteriorly. Quadrate small, with moderate-sizci~l suprastapedial process. Coronoid large, articulating with the splenial on the inner side. Humerus with strong radial process at distal end. Carpus and tarsus com- pletely ossified ; not more than six phalanges in any of the digits. Zygosphenes rudi- mentary or functional, chevrons fused with their centra. Clidastes, Cope (Edestosaurus, Marsh), (Figs. 242, 4. 6, 7, 251). Skull 0'4 to 0*7 m. long ; slender, tapering, depressed. Frontal not emarginate posteriorly in the median line. Parietal foramen entirely within the parietal plate. Teeth facetted on outer side, and smooth on the inner or on both faces. Dentary with about seventeen teeth, maxilla fifteen, pterygoid twelve to fifteen. Zygosphenes func- tional ; chevrons long. Neural spines elevated in posterior half of the tail, suggesting presence of a caudal fin. Upper Cretaceous ; Kansas, Alabama, and New Jersey. Mosasaurus, Conyb. (Leiodon, Owen; Pterycollasaurus, Dollo), (Figs. 243, 252). Skull attaining a length of U2 m., and total length of about 12 m. Distinguished from Clidastes chiefly by absence of a zygosphene-zygantrum arrangement. There are more than 130 vertebrae in the column, of which 46 are precaudal. The massive upper jaws are armed with about fourteen Fig. 251. Clidastes propython, Cope. Upper Cretaceous ; Umontown, Alabama. Skull, superior and lateral aspects, Vr. (after Co] e). 160 EEPTILIA class in powerful teeth on either side, and the pterygoids support about eight smaller Fig. 252. Mosasaurus camperi, v. Meyer. Upper Cretaceous ; Maestricht, Holland. Skull, lateral aspect, Via (after Uollo). teeth, all with anterior and posterior carinae. Upper Cretaceous ; Holland, Belgium, France, Northern Germany, and the United States. [The text for the preceding chapter on Pythonomorpha has been revised and modified in accordance with the latest researches by Dr. S. W. Williston, Professor of Geology and Palaeontology in the University of Kansas, at Lawrence. — Editok.] Sub-Order 3. LACERTILLA Saurii. Lizards. 1 Scali/, long - failed reptiles, with elongated and sometimes serpentiform body. Superior temporal arcade often wanting, and quadrate loosely attached to the cranium. Columella rod-like or rudimentary ; alisphenoid and orbit osphenoid not ossified. Mandibular rami suturally united at symphysis; teeth acrodont or pleurodonf. Sternum usually, and limb girdles ahvays present, but one or both pairs of appendages sometimes wanting. Limbs ambulatory, and usually provided with five clawed digits. The majority of lizards possess a dermal covering of corneous or in some cases of osseous scales, scutes, or spines, extending over the head and whole of the body. The vertebral column consists of numerous procoelous vertebrae (amphicoelous only among the Geckonidae and Uropeltidae), in which the neural arches are thoroughly coossified with their centra. There are seldom more than nine cervicals, and the atlas is composed of two dorsal pieces, either separate or united, and one ventral piece in the form of a free hypapophysis or intercentrum. Both the cervical and dorsal series have the transverse pro- cesses weakly developed, so that the ribs appear attached by a short tubercle. All of the ribs are single-headed. They are wanting on the anterior cervicals, some of the lumbar, and all of the caudal vertebrae. The sacrum is composed of two vertebrae. Stout transverse processes and chevron bones are borne by the caudals. A sternum is present, although sometimes rudimentary, in all lizards except Amphisbaena ; it usually occurs as a large rhombic or shield-shaped bone, sometimes pierced by two foramina. The ventral portion of the anterior 1 Literature : Cope, E. I)., The Vertebrata of the Tertiary Formations of the West (Rept. N.S. Geol. Surv. Territ. vol. III.), 1883. — Marsh, 0. ft, On Glyptosaurus, Tinosaurus, etc. (Amer. Journ. Sci. [3], vol. I. p. 456), 1871; and ibid. vol. IV. (1872), p. 298. — Meyer, H. con, Lacerten aus der Braunkohle des Siebengebirges (Palaeoutogr. vol. VII. p. 74), 1860. — Parker, W. K., On the structure and development of the skull in the Lacertilia (Phil. Trans, vol. CLXX. ), 1880. ORDER II SQUAMATA 161 dorsal ribs which join the sternum are sometimes cartilaginous, and in other cases bonv. The shall (Fig. 253) is distinguished from that of Rhynchocephalians chiefly by its large free quadrate, a delicate rod-like columella, and the con- stant absence of a lower and occasional absence of an upper temporal arcade. QuJ Col Ju Fig. 253. Monitor niloticus, Hassl. Recent; Egypt. Skull, lateral aspect, Vl- (col, Columella or epipterygoid ; exo, Exoccipital ; fr, Frontal ; ju, Jugal ; la, Lachrymal ; nix, Maxilla ; N, Narial opening ; no, Xasal ; pa, Parietal ; pi, Palatine ; pmx, Premaxilla ; prf, Prefrontal ; pro, Probtic ; pt, Pterygoid ; ptf, Postfrontal ; o/n, Quadrate ; 7*y> Quadrato-jugal ; S, Supratemporal vacuity ; so, Supraoccipital ; sq, Squamosal ; t, Transverse bone or ecto- pterygoid ; y, Superciliary), (after Cuvier). The vomer is unpaired, and not in contact with the pterygoids ; and the latter, together with the palatines, form a flat thin palate pierced by large vacuities. A transverse bone (ectopterygoid) occurs between the maxillae and pterygoids. The external nares are separate, and commonly placed near the orbits. The opisthotic is fused with the exoccipital, forming the so-called parotic process of the posterior temporal region. The distal end of this process serves with the posterior ends of the squamosal and prosquamosal as a buttress to which the movable quadrate is attached. The squamosal itself Fig. 254. Iguana tuberculata, Laur. Recent ; West Indies. Inner aspect of right ramus of mandible, showing pleuro- dont teeth, (ang, Angular; art, Articular; d, Dentary; fc, Coronoid ; op, Splenial ; s.ang, Surangnlar), (after Cuvier). is of small size and situated between the outer angle of the parietal and distal end of the prosquamosal. The postorbito- frontal unites with the forward end of the prosquamosal to form the lower border of the superior temporal fossa, and also unites with the jugal to form with this bone the posterior border of the orbit. In lizards the jugal is never in direct connec- tion with the quadrate. A parietal foramen occurs, and the parietal is frequently unpaired. The mandibular rami (Fig. 254) are suturally united at the symphysis ; they exhibit the same structure as in Pythonomorphs, except that there is no movable articulation behind the middle of each ramus. Teeth are always VOL. II M 162 KEPTILIA class in present in upper and lower jaws, and occur rarely on the palatines, pterygoids, and vomer. They are either acutely or obtusely conical, chisel- or arrowhead- shaped, serrated or carinated on the anterior and posterior edges, or in some cases their form may be hemispherical. Their bases are completely fused with the supporting bone, and their arrangement is either acrodont or pleuro- dont. Successional teeth are developed on the inner side of the functional ones, and gradually displace them. As a rule two pairs of limbs provided with five clawed digits are present, although the hinder pair may be rudimentary, and in some cases both pairs are wanting. The limb girdles persist, however, even among apodal forms, but the pelvic arch may become reduced. The coracoid is relatively large, and develops an anterior process, or precoracoid. The scapula also consists of two portions, of which the distal (suprascapula) is the larger and usually remains cartilaginous. The scapula proper is in some cases bifid at its distal extremity. The rod-shaped clavicle connects the anterior border of the scapula with the T-shaped or cruciform interclavicle, which is situated in front of the sternum. The bones of the fore-limb resemble those of Rhyn- chocephalians, except that the humerus never displays distal foramina. There are eight small carpals arranged in two rows, and the usual phalangeal formula is 2, 3, 4, 5, 3. Where the hind limb is normally developed, the ilia are movably attached to the cartilaginous ends of the sacral ribs. Pubes and ischia meet in a ventral symphysis, and the anterior border of the former frequently develops a strongly curved process. The femur generally exceeds the humerus in length, and the bones of the crus remain separate. The proximal tarsals consist of a large tibiale (astragalus) and fibulare (calcaneum) ; there are often but two free tarsals present in the distal row (Nos. III. and IV.), the remainder being fused with the metatarsals. The phalangeal formula of the pes is usually 2, 3, 4, 5, 4. Lizards of the present day are restricted almost exclusively to the tropical and temperate zones, and according to Hoffmann they comprise 434 genera and 1925 species. In comparison to these, the number of known fossil forms is very insignificant. The oldest remains commonly associated with lizards are the fragmentary jaws and procoelous vertebrae from the English Pur- beckian, known as Macellodus brodiei, but these are too imperfect for accurate determination. Most of the detached vertebrae and other fragments of Cretaceous age which have been referred to Lacertilians or Ophidians are probably Dolichosaurian. Even the known Tertiary fossils are very fragmentary, and belong for the most part to existing families. From the Lower Eocene of Wyoming repre- sentatives are known of the Varaniclae (Tinosaurus), Anguidae (Glyptosaurus, Saniva, Xestops), Iguanidae (Iguanavus), and Chamaeleonidae. Iguana itself, now restricted to the western hemisphere, occurs in the European Tertiary. Fragmentary remains of a number of other recent genera are found in the Eocene (or Oligocene) Phosphorites of Quercy, and Gypsum Beds of Apt, in France, among which may be mentioned the following : — Proiguana (Fig. 255), Plestiodofi (Fig. 256), Palaeovaranus (Fig. 257), Agama, Diploglossus, and Lacerfa. The Miocene also yields a number of Lacertilian fragments identifiable with recent genera, the principal localities being Auvergne, France ; the ORDER II SQUAMATA 163 lignites of Kott, near Bonn ; and the freshwater strata of Steinheim, Haslach, Gtinzburg, Sansan, and Colorado. The most gigantic of all lizards are Fi<;. 255. (.') Proigvana, sp. Phos- phorite of Quercy. Inner am I outer aspect of dentary, i/i- Pig. 256. Plestiodo n rait u rce a sis, Filhol. Phosphorite of Quercy. Inner aspect of dentary, Vi- Fig. 257. Palaeovaranus caylvxi, Filhol. Phos- phorite of Quercy. Maxillary frag- ment, Vi- Megalania and Notiosaurus, from* the Pleistocene river deposits of Queensland. The former is estimated to have been about 10 m. in length, and belongs to the Varanidae. Sub-Order 4. OPHIDIA. Snakes. 1 Body serpentiform, without limbs, covered with corneous scales. Vertebrae procoelous, with zygosphene-zygantrum articulation, and the anterior centra with strong simple hypapophyses. Both upper and lower temporal arcades, columella, sacrum, sternum, pectoral arch, abdominal ribs and haemapophyses are wanting. Parietal unpaired, without foramen, the sides extended downward and fused with the prootic, alisphenoid, and orbitosphenoid. Anterior portion of brain case completely ossified. Quadrate and pterygoid movably attached to skull by ligament. Maxillae and palatines usually freely movable, always displaceable. Premaxillae much reduced; mandibular symphysis ligamentous. Snakes are chiefty conspicuous for the absence of limbs. The body is greatly elongated, and the number of vertebrae very considerable, sometimes exceeding 400. The centra are concave in front and convex behind, the connection being by free ball-and- socket joints ; and their • articulation is further strengthened by zygapophyses and a zygosphene- zygantrum arrangement. The neural arches are thoroughly coossified with their centra. Simple hypapophyses are developed by the anterior ver- tebrae as far as sometimes the thirtieth, and the transverse processes are short and tumid (Fig. 258). Ribs are almost always present in the trunk region, beginning with the third vertebra ; and being freely articulated, are able to assist in propelling the body. They are long, curved, and frequently hollow • in the caudal region they are replaced by elongate trans- verse processes. Haemapophyses are wanting among snakes, and in their stead occur stout descending branches of the transverse processes (Fig. 259). 1 Literature : Cope, E. D., The Vertebrata of the Tertiary Formations of the West (Kept. U. S. Geol. Surv. Territ. vol. III.), 1883.— Filhol, II., Ann. Sci. Geol. vol. VIII. (1887). p. 27 '0.— Fischer, G., De serpentibus quibusdam fossilibus dissertatio. Bonn, 1857. — Meyer, II. von, Coluber atavus aus dem Siebengebirge (Palaeontogr. vol. VII.), 1860. — Rochebrune, A. F. de, Revision des Ophidiens fossiles (Nouv. Arch. Musee d'Hist. Nat. Paris [2], vol. III.), 1880.— Roemer, F., Ueber Python euboeieus (Zeitscbr. deutseb. geol. Ges. vol. XXII.), 1870. Python bivittatus, Schn. Recent: Sumatra. Anterior cervical vertebrae, i/i- ("r Atlas ; \xis ; hyp, Hypapophysis ; r, Rib; sp, Neural spine), (after d'Alton.) 164 REPTILIA CLASS II Fig. 259. bivittaius, posterior Python vertebra, c, Centrum : d, d'. The serpent cranium (Fig. 260) differs from that of lizards in the constant absence of both temporal arcades ; complete ossification of the anterior part of the brain case ; reduction of the premaxillae ; absence of a columella ; strong development of the ectopterygoid, which joins the maxillary and palato-pterygoid arches ; and movable connection between not only all of the last- named bones, but between the squamosal and occipital region, and between the rami of the lower jaw. The brain cavity is very long, and its lateral walls as far as the middle portion are formed by descending processes Caudal of the parietal and frontal. The exoccipital and opis- Trans- thotic are fused, and the maxilla is often much reduced. rng^raS^Xzygantru^" All the cranial bones are dense and ivory-like, and united by smooth sutures. Acicular, recurved, acrodont teeth are usually present on the maxillae, premaxillae pterygoids, palatines, and dentary bones. Occasionally they are wanting on the palatines (Uropel- tidae), and often also on the rudi- ™ - f r P ^ cs mentary premaxillae. In the N venomous snakes some of the maxillary teeth are hollow and traversed by a canal or groove Pmx ending in a slit-like opening at the end of the tooth. The canal is connected with the duct of a poison gland, and through it the secretion of the latter is forced when the animal strikes. Some of the non poisonous snakes also have grooved teeth immovably fixed to the maxillae. Locomotion among snakes is accomplished by the lateral move- ments of the vertebral column, assisted by the ribs, the latter being alternately pushed forward and the dermal scutes drawn after them. The Ophidia are distributed principally in the warmer regions, only the smaller forms extending into the northern temperate zone. By far the greater number are terrestrial, although some are amphibious, and a few are exclusively marine. About 400 recent genera and nearly 1800 species are known, as compared with only about 35 fossil forms, the majority of which are very imperfect. Most of the detached vertebrae of Cretaceous age originally regarded as Ophidian are doubtless Dolichosaurian, and the known Tertiary species are scarcely to be distinguished from those now living. Tolerably complete skeletons occur rarely in the freshwater Miocene of Oeningen and Euboea, as well as in the lignites near Bonn, and belong chiefly to the non-poisonous varieties. Typically Ophidian vertebrae (Palaeophis) from the Lower Eocene of Fig. 260. Crotalus horridus, Linn. Recent; South America, (art, Articular; bs } Basisphenoid ; d, Dentary; et, Ethmoid; /, Frontal ; mx, Maxilla ; n, Nasal ; ocb, Basioccipital ; ocl, Exoccipital ; ocs, Supraoccipital ; p, Parietal ; %rf, Post- frontal ; pi, Palatine ; pmx, Premaxilla ; pr, Prootic ; prf, Prefrontal ; pt, Pterygoid ; qu, Quadrate ; sq, Squamosal ; tr, Transverse or ectopterygoid), (after Claus). ORDER III ICHTHYOSAUEIA 16; Sheppey and Bracklesham, England, and Cuise la Mothe France, are ascribed to marine Pythonidae which may have attained a length of 6 m. A vicarious genus, Titanophis, occurs in the Eocene of New Jersey, and several genera (Helagris, Cope; Boavus, IAthophis, and Limnophis, Marsh) have been described from the Eocene of Wyoming and New Mexico. Among the Upper Eocene (or Oligocene) forms of France, Switzerland, and England may be mentioned Palaeopython (Fig. 261) and Scytalophis, Rochebrune, and Paleryx, Owen. za Palaeopython cadurcensis, Filhol sp. Phosphorite of Quercy, France. A, Anterior. B, Lateral. C. Inferior. D, Posterior aspect of vertebra, l/i- ( c > Centrum ; d, Transverse process with costal tubercle ; sp, Neural spine ; :. Zyapophysis : za, Zygantrum ; zsp, Zygosphene.) One of the best preserved Miocene serpents is Heteropython euboeicus, Roemer, from Kumi, on the island of Euboea. Representatives of the Colubridae (Elaphis, Aldr. ; Coluber, Linn.), and Erijcidae (Scaphojrfiis, Roch.) have been described from the freshwater Miocene of Oeningen, Steinheim, Giinzburg, Haeder, Weisenau, Ulm, Sansan, Touraine, and other localities, as well as from the lignites of Rott, near Bonn. A number of Erycidae and Crotalidae are also known from the Miocene of Colorado and Oregon. All known Pleistocene remains are identifiable with existing genera. Order 3. ICHTHYOSAURIA. (Ichthyopterygia. 1 ) Primitive marine reptiles with fish-like body, long head and tail, and no distinct neck. Investing bones of temporal region contracting into a single broad arcade ; quadrate fixed. Rostrum long and tapering ; orbits large, laterally placed, with sclerotic ring. External naves separate, slightly in advance of orbits. Parietal foramen and supra- temporal vacuities large. Teeth acutely conical, inserted in a continuous groove on the maxillae and elongated premaxillae and mandibles, but sometimes wanting. Vomer edentulous. Vertebrae numerous, very short, deeply amphicoelous. Bibs long, abdominal ribs present, but sternum absent. Pectoral arch consisting of coracoids, ■scapulae, clavicles, and a T-shaped inter clavicle. Limbs short, paddle-shaped, sometimes with more than five rows of phalanges, and a layer of cartilage around the carpals, tarsals, and phalanges. No dermal armour. 1 Baur, G., On the morphology and origin of the Ichthyopterygia (Amer. Nat. vol. XXI. p. 837), 1887; also Bericht, 20th Versammlung Oberrhern. geol. Vereins (1887), p. 20; and Anat. An/.. vol. X. (1894), p. 456. — Cope, E. D., On the cranium of Ichthyopterygia (Proc. Amer. Assoc. Adv. Sci. vol. XIX. p. 197), 1870.— Fraas, E., Die Ichthyosaurier der suddeutschen Trias mid Jura Ablagerungen. Tubingen, 1891. — Die Hautbedeckung von Ichthyosaurus (Wiirtt Jahresh. p. 493), 1894. — Hawkins, T., Memoirs of Ichthyosauri and Plesiosauri. London, 1834.— Marsh, 0. C, On Baptanodon, etc. (Amer. Journ. Sci. [3], vol. XVII. p. 86), 1879 ; also ibid. vol. XIX. (1880), p. 491 ; and vol. L. (1895), p. 405. — Merriam, J. <'., Triassic Ichthyopterygia (Bull. Californ. Univ. vol. III. p. 63), 1902.— Owen, R., Monograph of the fossil Reptilia of the Liassic Formations, Part III. (Palaeontogr. Soc. ), 1881. — Monograph of the fossil Reptilia of the Cretaceous Formations {ibid.), lSh.—Seeley, H. G., On Ophthalmosaurus, etc. (Quar. Journ. Geol. Soc. vol. XXX. p. 696), 1874.— On the skull of an Ichthyosaurus (ibid. vol. XXXVI. p. 635), 1880.— Theodori, C, Beschreibung des kolossalen Ichthvosaurus trigonodon zu Banz. Munich, 1854. 166 KEPTILIA CLASS III The members of this order differ conspicuously from all living reptiles, and are distinguished chiefly by their fish-like form of body, paddle-shaped limbs with numerous oval or polygonal phalanges, large head with elongated rostrum, short amphicoelous vertebrae, and naked integument. The snout resembles that of a dolphin, the teeth are crocodilian-like, the skull and pectoral girdle suggest those of lizards, the limbs are very similar to the flippers of marine mammals, and the vertebrae and caudal fin are decidedly fish-like. As regards external form, limb-structure, and adaptation to a marine existence, they depart as widely from other reptiles as whales do from land mammals, and occupy as isolated a position. The absence of branchial arches and shape of the hyoid bones prove that respiration was pulmonary among Ichthyosaurs ; and their viviparous habit is demonstrated by a number of well-preserved skeletons in the Lias of England and Wiirtemberg, which exhibit as many as seven embryonic individuals in the abdominal cavity. Large quantities of their coprolites occur in various localities, and contain the scales and bones of fishes, and fragments of cephalo- poda. Ichthyosaurian remains are found exclusively in the marine deposits of the Mesozoic, and are most abundant in the Lias. Of their origin nothing is known, although it is certain that they were derived from land animals. The earlier (Triassic) forms have less completely paddle-shaped extremities than the later. Some species attain a length of 9 m., and the smallest are only about 1 m. long. The skull (Fig. 262) is conspicuous for its elongated, dolphin-like rostrum and enormous orbits, which are surrounded by a ring of fifteen to nineteen scler- ang Fig. 262. Ichthyosaurus acutirostris, Owen. Upper Lias; Curcy, Calvado.s. Skull, superior and lateral aspects, V* ■ I, Orbit; ang, Articular; d, Dentary ; fr, Frontal; j, Jugal ; k, Surangular; md, Mandible; mx, Maxilla; A, External narial opening ; na, Nasal; op, Splenial ; pa, Parietal ; pmx, Premaxilla; por, Postorbital ; ptf, Post- frontal ; qnj, Quadrato-jugal ; S, Supratemporal vacuity ; scl, Sclerotic plates ; sq, Squamosal ; st, Suprateniporal or prosqnamosal (after E. Deslongchamps). otic plates. The paired parietals and frontals are of small size, and a large parietal foramen occurs at their junction in the median line. Adjoining the parietals on either side are the large oval supratemporal vacuities (S), bounded ORDER TIT ICHTHYOSAURIA 167 externally by the squamosal and postfrontal. The external nares are triangular and placed close to the orbits ; the nasals are extended in front, and the premaxillae greatly produced. The superior border of the orbit is formed by the postfrontal, and prefrontal, the latter a narrow, triangular plate. In front of the orbit, and separating it from the narial opening, is a triangular lachrymal. A long, slender, rod-like jugal bounds the orbit below, and a curved oblique postorbital encloses it behind. Joining the postorbital and jugal posteriorly is the quadrato-jugal, which forms the postero-lateral angle of the skull, and together with the quadrate furnishes the connection for the lower jaw. An irregularly triangular or rectangular plate, the supratemporal (or prosquamosal, St), is inserted between the quadrato-jugal and squamosal, and behind the postorbital and postfrontal. The maxilla is an elongate triangular bone, inserted between the jugal, lachrymal, and premaxilla. The basioccipital (Fig. 263) is very strongly developed, and bears a stout articular condvle. Above it and on either side of the foramen magnum are the paired exoccipitals, capped by the supraoccipital. Adjoining the ex- occipitals are the opisthotics, which remain separate from the prootics. The bones of the occipital and otic y; A CUJ Ichthyosaurus acutirostris, <>wen. Upper Lias ; England. Skull, posterior aspect, 1 / i . (bo, Basi- occipital condyle; exo, Exoccipital on either side of foramen magnum ; j, Quadrato-jugal ; pa, Parietal ; pt, Pterygoid; characters of the order. Trias to Cretaceous. Mixosaurus, Baur. Most of the smaller- sized Triassic remains are placed in this genus as distinct from Ichthyosaurus, the teeth being in less uniform series, and the limbs less completely paddle-shaped. The radius and ulna are elongated, and separated by an interstice throughout their length. M. cornalianus, Bassani, the typical species, varies from 0*5 to 1 m. in length, and occurs in the Upper Trias of Besano, Lombardv. M. atavus, Quenstedt, is known by fragments from the Muschelkalk of Wiirtemberg. Ichthyosaurus, Konig (Figs. 262-271). Teeth conical and in uniform series. Radius and ulna shorter than broad, proximally in contact. Humerus and femur with two concave distal facettes. Total length of largest forms upwards of 10 m. This genus is most abundant in the Lias, /. communis and I. intermedins being familiar English species. Localities noted for the excellence of their fossil remains are Dorsetshire (Lyme Regis) and Somersetshire in the Lower Lias, and Yorkshire, Cal- vados, Wiirtemberg (Boll, Holzmaden), and Franconia (Banz, Altdorf) in the Upper Lias ; and the species of the one division are for the most part distinct from those of the other. /. communis, intermedins, latimanus, platyodon, and tennirostris are esjjecially characteristic of the Lower Lias, and I. acutirostris, ingens, quadricissus, and trigonodon of the upper member. Remains of Ichthyosaurus are sparse in the Middle Jura, but a number of species occur in the Upper Jura of Solenhofen and Kelheim, Bavaria, Northern France, and England. Cretaceous forms are known from England, France, the East Indies, Australia, New Zealand, and Chili. Ophthalnwsaurus, Seeley. Edentulous or with minute teeth confined to front of the jaw. Humerus and femur with prominent trochanteric ridge and with three concave distal facettes ; all remaining limb bones more or less rounded and separated. Clavicles separated. Upper Jura and Lower Creta- ceous ; England. Baptanodon, Marsh (Sauranodon, Marsh non Jourdan). Similar to the preceding, but completely edentulous. Interclavicle not observed ; digit arising from the intermedium consisting of two longitudinal rows of ossicles. Coracoids unite in the median line in large elliptical facettes. Upper Jura : Wyoming. Shastasaurus, Merriam. Includes several large species from the Upper Trias of northern California. Pelvis very robust ; all but first ten ribs single- headed. ( [i/mbospondylus, Leidy, from Middle Trias of Nevada, is imperfectly known. Order 4. SAUROPTERYGIA. Owen. 1 Primitive aquatic reptiles with long neck, lizard-like body, and moderately short tail. Cranium small, with parietal foramen mid large supratemporal vacuities. 1 .1 nil revs, (J, IT., On Plesiosaurus. Pliosaums, etc. (Quar. Journ. (Vol. Soe. vol. XXXVJI. p. -440). 1881. — Also ibid. vol. LIII. (1897), p. 177, and various articles in (Vol. Mag. [4], vol. II. (1895), p. 241 ; ibid. vol. III. (1896), p. 145 ; Ann. Mag. Xat. Hist. [6], vol. XV. (1S95), p. 333 : ibid. vol. XVI. (1895), p. 429. — Bassani, F., Sui fossili degli schisti bituminosi triassici
  • W® ^4M / w^ Fig. 280. Plesiosaurvs dolichodi irus, Conyb Regis; Dorsetshire. Skeleton, Hawkins). Lower Lia ventral aspect, ] lis Lyme (after 178 REPTILIA CLASS III head and short neck. Skull depressed and narrow, attaining a length of 1*3 m. Internal nares remotely situated, mandibular symphysis considerably extended. Margin of upper jaw on either side with a series of about thirty powerful carinated teeth, sometimes 25 cm. long ; the crown traversed for a portion of its height by strong elevated ridges. About twenty very short cervicals with double-headed ribs. Limb girdles similar to those of Plesiosaurus. Lias to Upper Jura ; England, Northern France, Switzerland, Bavaria, Russia, and India. Megalneusaurus } Knight. Largest known Plesiosaur, the humerus attaining a length of 1 m., or about one-half the length of the entire fore-limb, and articulating only with the radius and ulna. The latter bones are polygonal and closely applied against each other and the three proximal carpals. Coracoids produced in front of the glenoid cavity ; vertebrae elongated. Upper Jura ; Wyoming. M. rex, Knight. Elasmosaurus, Cope (Fig. 282). A skeleton in Philadelphia lacking the head exceeds 13 m. in length. The seventy-two cervicals are longer than deep, and bear short, single-headed ribs. The neural arches are all fused with their centra, but the chevron bones are articulated with the caudals. Pectoral arch similar to that of Oryptoclidus. Limbs and greater part of the skull unknown. Upper Cretaceous ; Kansas. Dolichorhynchus, Willist. Head long, snout very slender ; mandibular symphysis much elongated; teeth small, numerous; vomers very long ; posterior nares small, included between vomer and pala- FiG. 281. Plioscmrus grandi Owen. gian ; Tooth, Owen). tines ; niina : Kimmerid- Dorsetshire. i/ 4 (after no posterior palatine fora- pterygoids contiguous only at extremities. Neck shorter than head ; cervical ribs single-headed ; axis with ribs ; nineteen cervicals and about thirty dorsals are pre- sent ; tail very short, conical. Clavicular arch complete, the clavicles articulating with the long precoracoidal process. Ischium elongate. Humerus and femur moderately expanded ; three pro- podials. Known by a nearly com- plete skeleton about 3 m. in length from the Niobrara Cretaceous of Kansas. Polyptychodon, Owen (Fig. 283). Imperfectly known, teeth resembling those of Pliosaurus, but with more prominent coronal ridges, some of which extend to the apex. Middle and Upper Cretaceous ; England, Germany, and Russia. Fig. 282. Elasmosaurus platyurus, Cope. Upper Cretaceous ; Kansas. Pectoral arch, shaded parts restored ; greatly reduced, cor, Coracoid ; so, Scapula (after Cope). Fig. -283. Polyptychodon inter- ruptus, Owen. Ceno- manian ; Kelheim Bavaria. Tooth, 1 /j. order V THEROMORPHA 179 Order 5. THEROMORPHA. Cope. (Anomodontia, Seeley, non Owen.) l Primitive laud reptiles with more or less biconcave vertebrae and limbs adapted for habitual support of the body. Investing bones of temporal region either funning a continuous shield or contracting into a single broad arcade, sometime* irregularly perforated. Quadrate fixed, often reduced in size. Pineal foramen present. Teeth thecodont, occasionally wanting. Pectoral arch with well -developed epicoracoids (/>recoracoids), clavicles, and T-shaped interclavicle, besides scapulae and coracoids. All the elements in both limb girdles either fused or immovably united by suture. Humerus ivith entepicondylar foramen and prominent delto-pectoral crest. Extremities pentadactylate. Sacrum consisting of two to six vertebrae; anterior ribs completely or imperfectly double-headed, abdominal ribs wanting. Many widely dissimilar characters are exhibited by the various groups of ancient reptiles, which have received the general designation of Theromorpha, in allusion to their resemblance in certain skeletal peculiarities to the lowest mammals (Monotremata). They are also often called Anomodonts, on account of their remarkable dentition. There can be no doubt that these creatures occupy an intermediate position between the highest Labyrinthodonts, such as Mastodmisaurus, and monotreme mammals ; and it is altogether probable that from amongst some of their number with one robust zygomatic arch and triconodont teeth, the Mammalia arose. Theromorphous reptiles represent not only a transitional stage between mammals and amphibians, but they form a collective group, uniting in them- selves characters that are elsewhere found distributed amongst various subdivisions of both reptiles and mammals. No other reptilian order has the three elements of the pelvic arch on each side fused into an innominate bone, as in mammals. The intimate union of the bones of the pectoral arch is paralleled among the Salamandridae and Sauropterygia ; and the sacrum, formed sometimes of a number of vertebrae, resembles that of Dinosaurs and mammals. The differentiation of the marginal teeth into incisors, canines, and molars, and the occasional development of a strikingly mammalian form of limb {Therio- desmus) and a tripartite or even dicondylic basiocciput (Cynognathus), are significant characters. A distinguishing feature between this order and Sguamata is the fixation of the quadrate ; and the absence of a lateral temporal vacuity, with an arcade above and below, distinguishes it from all other ArcJtosauria (Rhynchocephalians, Dinosaurs, Crocodiles, and Pterosaurs). The term Anomodontia, although restricted by Owen to the group of Dicynodonts, is made synonymous by some authors with Theromorpha, or Theromora, as they are sometimes called. 1 Literature : Cop*. /•;. /;., The Reptilian order Cotylosauria (Proc. Amer. Phil. Soc. vol. XXXIV. p. 436), 1896. -—Ibid. vol. XXXV. (1896), p. 122.— Newton, E. T., Some new Reptiles from the Elgin Sandstone (Phil. Trans, vol. CLXXXIV. p. 436), 1893.— Owen, R., On Dicynodon (Trans. Geol. Soc. vol. VII. p. 59), 1845. — On some Reptilian fossils from South Africa (Quar. Journ. Geol. Soc. vol. XVI. p. 49), I860.— Ibid. vols. XXXII. (1876), p. 95 ; XXXVI. (1880), p. 414 ; XXXVII. (1881), p. 261 ; and XL. (1884), p. 146.— On Dicynodont Reptiles (Phil. Trans, vol. CLII. p. 442), 1862.— Catalogue of the fossil Reptilia of South Africa in the British Museum. London, 1876. — Seeley, II. G., Researches on the Anomodont Reptiles and their allies (Phil. Trans, vol. CLXXIX. p. 59), 1888. — Ibid. vols. CLXXX. (1889), p. 215 ; CLXXXIII. (1892), p. 311 ; CLXXXIV. (1893), p. 488 ; CLXXXV. (1894), p. 987 ; and CLXXXVI. (1895), p. 59. Also Ann. Mag. Nat. Hist. [7], vol. i. (1898), p. 164, and Quar. Journ. Geol. Soc. vol. LVI. (1900). 180 KEPTILIA CLASS III Sub-Order I. PAREIASAUEIA. Seeley. (Cotylosauria, Cope.) Head completely covered by a bony roof ; 'parietal foramen large ; narial openings separate. Marginal teeth arranged in a more or less uniform series. Vertebral centra pierced for the persistent notochord. The skeletal characters of this group proclaim a very close relationship with the higher Labyrinthodont Amphibians. In the typical genus, Pareia- saurus, the external bones of the skull are sculptured, but no true mucous canals have been observed. Family 1. Pareiasauridae. Cope. Teeth conical, or with compressed, cuspidate crown, those on the margin of the jaws arranged in close regular series. Smaller teeth usually present on palatines, pterygoids, and vomers. Pelvic bones fused in the adult. Limbs short and stout. Permian and Trias. Pareiasaurus, Owen (Fig. 284). Known by tolerably complete skeletons over 2 "5 m. long from South Africa and Northern Russia. Skull broad, depressed, and triangular in form, the external bones coarsely sculptured, but their sutures not clearly distinguishable. Orbits relatively small, laterally Pareiasaurus bat id, Seeley, Fig. 2S4. Karoo Formation (Permian or Trias) ; Tainbor Fontein, Cape Colony. Skeleton ; 1/20 (after Seeley). placed. Occipital condyle slightly indented. Bones of the palate fused, and bearing several series of small teeth. There are about eighteen presacral vertebrae, each with a deepened articulation for the single -headed ribs. Small intercentra occur between all the dorsal vertebrae ; the four sacrals are not fused. About thirty caudal vertebrae, the anterior ones with short ribs, and nearly all with neural arches and chevron bones. Scapula very long, like that of Dinosaurs. Coracoid small and subrectangular, epicoracoid narrow and triangular ; clavicles robust, meeting in the middle line and resting on the front border of the large T-shaped interclavicle. A supraclavicle also said to be present on each side. Humerus short, massive, expanded at the ORDER V THEROMORPHA is] ends ; epicondylar foramen not observed. Ulna very stont, with prominent olecranon process. Pelvic bones massive, coossified ; acetabulum closed. Hind limb slightly shorter than the fore, and digits rather smaller ; the five ungual phalanges clawed. P. bombifrons, P. serridens, Owen ; P. baini, Seeley. ? Tapinocephalus, Anthodorij Owen. , Karoo Formation; South Africa. Elginia, Newton. Known only by the skull, which is about 15 cm. long, triangular, coarsely sculptured, and provided with a number of paired bosses and spinous or horn-like defences. These occur along the posterior and lateral margins, and on the parietal, frontal, and nasal elements. Teeth with slightly constricted base and serrated crowns. Supposed Trias of Elgin, Scotland. Procolophon, Owen (Fig. 285). Skull about 5 cm. long, short and tri- angular, not externally sculptured. Orbits greatly enlarged, and temporal / ' Fig. 2S5. Procolophon- triguaiceps, Owen. Karoo Formation (Permian or Trias); South Africa. Restoration of skull from superior (A), inferior (B), and lateral (C) aspects, also part of the pectoral arch, slightly reduced, ac, Glenoid cavity for humerus ; bs, Basisphenoid ; co, Coracoid ; ecpt, Ectopterygoid ; epco, Epicoracoid ; /. Frontal ; icl, Interclavicle ; ipt, Interpterygoid vacuity ; j, Jugal ; I, Lachrymal ; Itf, Lateral temporal vacuity ; md, Mandible; mx, Maxilla ; na, Nasal; nor, Anterior nares ; orb, Orbit; p, Downward ectopterygoid proa pa, Parietal ; pin, Pineal foramen ; pi, Palatine; pmx, Premaxilla ; prf, Prefrontal; pt, Pterygoid ; ptna, Pos- terior nares ; ptf, Postfrontal ; pto, Postorbital ; qj, Quadrato-jugal ; qn, Quadrate ; st, Supratemporal or pro- squamosal ; sq, Squamosal; r, Vomer (from A. S. Woodward). arcade pierced by a slight vacuity. Teeth conical ; a series of minute teeth present on vomer and pterygoids. Interclavicle T-shaped, with elongated arms ; epicoracoid notched. Karoo Formation ; South Africa. Aristodesmus, Seeley. Lower Trias; Switzerland. ? Phanerosaivrus, v. Meyer. Permian ; Saxony. Family 2. Pariotichidae. Cope. Teeth in more than one series in one or both jaivs, and with cylindric roots ; vertebrae ossified. Permian. Otocoelus, Cope. Skull about 12 cm. long, externally sculptured, but without bosses. Dorsal carapace consisting of a series of twelve or more 182 EEPTILIA CLASS III transversely elongated bands of bone alternating with the ribs. Permian ; Texas. 0. testudineus, Cope. Pariotichus (Ectocynodon), Isoclectes, Pantyhcs, Hypopnous, Cope. Texas. Family 3. Diadectidae. Cope. Anterior teeth obtusely conical, the other marginal teeth laterally expanded, with tumid bases and inner and outer cusps of unequal height. Vomer with minute teeth. Basioccipital loosely articulated. Permian. Empedias, Cope (Empedocles, Cope). Skull triangular, 50 cm. long. Sacrum of two vertebrae ; pelvic bones fused. Permian ; Texas. Diadectes, Chilonyx, Bolboden, Cope. Permian ; Texas. Sub-Order 2. THERIODONTA. Owen. (Cynodontia, Owen.) Investing bones of temporal region contracting into a single broad arcade, sometimes irregularly perforated ; supratemporal vacuity large, quadrate small. External bones not sculptured. Occipital condyle bilobate ; premaxillae separate; marginal teeth differentiated into incisors, canines, and molars. External, nares terminal, separate, or undivided; internal openings displaced backwards, owing to development of secondary palate. The skull of Theriodonts is remarkably similar in form to that of car- nivorous mammals, and the dentition exhibits modifica- tions unusual among reptiles. The mandible bites within the upper jaw, and the lower canines cross in front of the upper as in mammals. Owing to the development of a secondary or false palate by plates from the maxillae and palatines, the opening of the internal nares on the roof of the mouth is displaced back- ward, as in crocodiles and mammals. An approach to the dicondylic condition of the mammalian skull is also frequently observed. The skeleton of the trunk and limbs is imperfectly known. Pt Bo Pa Fig. 286. Galesaums planiceps, Owen. Karoo Formation; Basutoland. South Africa. Skull, slightly restored, from lateral (A), palatal (/-'), and superior (C) aspects, Va- A Posterior tooth, enlarged. ", orbit; bo, basioccipital; eh, Posterior nares; Jr, Frontal; md, Mandible ; mx, Maxilla ; N, Anterior narial opening ; na, Xasal ; /in. Parietal ; prf, Prefrontal ; pt, Pterygoid (after Owen). Family 1. Galesauridae. Lydekker. Palatal teeth insignificant or wanting ; external narial Trias. openings confluent or separated ; limb bones slender. Galesaurus, Owen (Xythosaurus, Owen), (Fig. 286). Known only by the ORDER V THEROMORPHA 183 skull, which is less than 10 cm. long, and has the nares divided by a median septum. Four incisors above and three below, with one canine and a number of tricuspidate molars in each jaw. Karoo Formation ; South Africa. Lycosaurus, Owen (Fig. 287). Like the preceding, except that the molari- form teeth are all simple cones, though more or less compressed and with finely serrated edges. There are about five of them on each side above and below. Karoo Formation ; South Africa. Aelurosaurus, Owen. Differs from Lycosaurus in having small, pointed teeth irregularly grouped on anterior half of the palate. Same horizon. Cynognathus, Seeley. Skull remarkably mammalian - like, about 40 cm. long, with divided nares and two prominent convex condyles below the foramen magnum, composed chiefly of the exoccipitals. There are four serrated incisors in the upper and three in the lower jaw ; and one canine and nine molars above and below on each side. Six cervicals, eighteen dorsals, five lumbars, and three or four sacrals. Accompanies the preceding. C. crateronotus, Seeley. Ci/nochampsa, Cynodraco, Cynosuchus, Gorgonops, Tigrisuchus, Owen. Founded on more or less imperfect remains from the Karoo Formation of South Africa. Fig. 287. Lycosaurus curvimola, Owen. Karoo Formation ; Kugaberg, Cape Colony. Skull, lateral aspect, 1/3. «, Orbit; '/. Mandible (after Owen). Family 2. Deuterosauridae. Seeley. Ca ni nes large, with serrated anterior and posterior margins; no palatal teeth. Sacrum of two anchylosed vertebrae. Ribs double-headed. Scapula flat ; ilium not produced anteriorly ; acetabulum closed. Permian; Russia. Deuterosaurus, Eichw. Skull with a median crest ; incisors large and transversely compressed. Lachrymals greatly developed ; quadrate large ; scapula distally expanded. Bhopalodon, Fischer. Like the preceding, but with serrated incisors, and lanceolate molars behind the canines. Supratemporal vacuity very small ; sclerotic ring present. The fragmentary remains described as Brithopus, Orthopus, and Syodon by Kutorga, and Dinosaur us by Fischer, are probably identifiable with the above genera, which they accompany. Cliorhizodon, Twelvetrees, is of uncertain position. Family 3. Tritylodontidae. Cope. Snout broad anil obtuse. A pair of large incisors or canine-like teeth in front, apparently growing from a persistent pulp. Molariform teeth bearing two or three longitudinal series of tubercles. Poster'mr mires remote, and roofed over by secondary palate. Quadrate reduced. Trias. 184 REPTILIA CLASS III This family is regarded by Seeley as typical of a distinct order of reptiles, Gomphodontia, and ancestral to mammals. Tritylodon, Owen (Fig. 288). Known by small, decidedly mammalian-like crania. Karoo Formation; South Africa. Gomphognathus, Diademodon, Mi- crogomphodon, Tri- rachodon, Seeley. The first -named has a double occipital condyle, Fig. 288. Tritylodon longaevus, Owen. Trias; Taba-chow, Basutoland, South Africa. Skull from superior and palatal aspects, 2/ 3 (after Owen). Fig. 289. THglyplius fraasi, Lyd. Upper Trias : Hohenheim, Wurtem- berg. Upper molar, 1/1 and 2/j (after Fraas). and its single zygomatic arch resembles that of mammals. Theriodesmus, Seeley, is known by a remarkably mammalian-like fore-limb and manus. Karoo Formation ; South Africa. Triglyphus, Fraas (Fig. 289). Known only by minute teeth from the Upper Triassic Bone-bed of Hohenheim, near Stuttgart. Sub-Order 3. ANOMODONTIA. Owen. (Dicynodontia, Owen.) Investing bones of temporal region contracting into a single broad arcade, formed principally by the enormously developed squamosal. External bones not sculptured ; supratemporal vacuity large; quadrate small; premaxillae fused; external nares separated. Jaws edentulous, or with a single pair of tusk-like teeth in the maxillae set in deep alveoli and growing from persistent pidps. Cervical ribs double-headed, dorsal single-headed. Sacrum of five or six vertebrae. The Anomodonts or Dicynodonts are mostly large terrestrial reptiles of Triassic age, of which no complete skeletons have yet been discovered, but numerous crania, vertebrae, and other fragments are known from South Africa, East India, Ural, and Scotland. The vertebral column consists of seven or eight cervical, twelve or thirteen dorsal, five or six sacral, and about twenty caudal vertebrae. The centra are short and slightly amphicoelous. Double-headed ribs are borne by the cervical, and single-headed ribs by the dorsal vertebrae. The cranial sutures (Fig. 290) are frequently obscure and difficult to determine. The brain cavity is very small and the surfaces for attachment of the muscles of the jaw unusually large. On either side of the upright occiput is an enormously developed squamosal, which forms the greater part of the single temporal arcade, and is ORDER V THEROMORPHA is;, fused with the small quadrate below. A foramen is enclosed by the parietals, which are small, and sometimes much reduced. The frontal and prefrontal form the superior border of the orbit, and the maxilla, lachrymal, and pre- frontal the anterior. The orbits are laterally placed in about the middle of the skull, and in one genus (Ptychognatkus) traces of a sclerotic ring have been observed. A narrow, curved bar, the postorbital, separates the orbit from the supratemporal vacuity, and the lower orbital boundary is formed by the maxilla together with a very massive jugal. The nasals are steeply inclined toward the front, and form with the Pinx unpaired premaxilla a sometimes elon- gated rostrum. Small internasals are occasionally present below the anterior nares, which are placed laterally at the junction of the nasals, lachrymals, and premaxillae. The oral border of the I'm r, Fig. 290. latter forms a sharp, cutting edge, and was probably sheathed during life of the animal by a corneous layer, as in Chelonians and Aves. A pair of powerful, decurved, tusk-like teeth, one on each side, is developed by the maxillae, and the deep alveoli in which they are seated are indicated by an external folding of the plate. Even among toothless forms alveoli are present, but are occupied by osseous substance. The basioccipital is short and takes part in the occipital condyle. In front of it on the lower side (Fig. 291) is placed a subrectangular basisphenoid which joins the very large pterygoids. The latter meet in the middle line, but leave a small interpterygoidal vacuity behind the narrow vomer. The backwardly 186 REPTILTA CLASS III directed internal nares are scarcely if at all covered by a secondary develop- ment of the palatine plates. The mandible is without a coronoid process, and the rami are fused at the symphysis. Their oral borders are sharp, and were probably once encased in horn. Pmx Fig. 291. Pig. 292. Dicynodon pardiceps, Owen. Karoo Formation; Fort Beaufort, Cape Dicynodon pardiceps, Owen. Colony. Palatal aspect of skull, i/ 4 - '"'> Basioccipital ; c, Maxillary tusk Anterior aspect of humerus, !/ 4 . (fractured); ju, Jugal ; mx, Maxilla; pmx, Premaxilla ; pi, Palatine; pt, b, Delto-pectoral ridge ; e, Entepi- Pterygoid ; qu, Quadrate (after ( )wen). condylar foramen (after Owen). The scapula is a very long bone, similar to that of Monotreme mammals. It bears an acromial process and is attached by its proximal end to the cora- coid and epicoracoid. The humerus is short and excessively stout, with an entepicondylar foramen ; ulna Fig. 293. Eurycarpus oweni, Seeley. Karoo Formation ; Schneebergkette, Cape Colony. Left fore-limb with impression of dermal covering, 1/3 (after Owen). Fig. 294. Platypodosaurus robustus, Owen. Karoo Forma- tion ; Cape Colony. Ventral aspect of sacrum and right half of pelvis, il, Ilium ; isch, Ischium ; o, Obturator foramen : pu, Pubis ; s 1 — s 5 , Sacral vertebrae. and radius are separated. In the pelvic arch the three elements of each side are fused into an innominate bone which joins its fellow in a median order v THEROMORPHA 187 symphysis. The femur and cms are somewhat longer than the corresponding bones of the fore-limb. Dicynodon, Owen (Figs. 291, 292). Skull attaining a length of 0'5 m. Transition from parieto-frontal to nasal region gradual ; maxillae with a pair of tusk-like teeth. Abundant and represented by over a dozen species in the Karoo Formation of South Africa. Oudenodon, Owen. Like the preceding, but toothless ; possibly referable to females of Dicynodon. Ptychognathus, Owen (Lystrosaurus, Cope), (Fig. 290). Frontal and nasal regions sloping at a sharp angle from top of the skull. Smaller than Dicynodon, which it accompanies. Gordonia, Newton. Form of skull similar to Dicynodon, but much smaller, with more delicate bones and diminutive teeth ; premaxilla nearly vertical. Supposed Trias of Elgin, Scotland. Geikia, Newton. Resembling Ptychognathus, but toothless. Elgin Trias. Eurycarpus, Seeley (Fig. 293); Keirognathus, Seeley ; Theriognathus, Titano- suchus, Platypodosaurus (Fig. 294), Owen. All founded on fragmentary remains from the Karoo Formation of South Africa. Sub-Order 4. PLACODONTIA. von Meyer. 1 Bones of temporal region forming a single broad arcade ; supratemporal vacuity large, opening superiorly; orbits and external nares laterally placed; the latter separate and remote. Palate with a paired longitudinal series of pavement teeth, and similar ones present in single series on the dentary. Anterior teeth above and below eylindro-conical ; maxillae with a series of depressed, conical, or molariform teeth. Placodonts are remarkable for their peculiarly modified dentition, which is unparalleled among reptiles. The pavement-like crushing teeth of the palate and lower jaw attain considerable size, and exhibit flat or slightly arched crowns, usually dark- coloured, and smooth or finely wrinkled. They are replaced by successional teeth developed beneath them. The skull is similar in form to that of Dicynodonts and certain Therio donts ; and as in these groups the temporal and jugal arches unite to form a single, broad, bony arch across the postero-lateral region of the cranium. The quadrate is fused with the squamosal and jugal, and exposes a prominent transverse condyle. On the under side the palatines and pterygoids unite to form an extensive bony palate for the support of the pavement teeth. The internal nares are placed far forwards, but the external openings and orbits occupy similar positions to those in Dkynodon. Of the rest of the skeleton nothing is known. The detached teeth were for a long time confounded with fishes, until their reptilian nature was demonstrated by Owen. All the remains are from the marine Trias of central Europe. Placodus, Agassiz (Figs. 295, 296). Skull not much longer than broad, superiorly arched, the snout somewhat produced. Premaxillae and symphysis of lower jaw with eylindro-conical incisors. On either side of the palate and 1 Literature : Meyer, II. von, Unterkiefer vou Placodus andriani (Palaeontogr. vol. X. p. 59), 1862. — Ibid. vol. XI. 1863.— Monster, G. von, Ueber eiuige ausgezeichnete fossile Fischzalme aus dem Muschelkalk bei Bayreuth. 1830. — Ueber Placodus rostratus (Beitrage zur Petrefaktenkunde, pt. 4), 1843. — Oioen, 11. , Description of the skull and teeth of Placodus laticeps (Phil. Trans, vol. XLIX.), 1858. 188 KEPTILIA CLASS III on the dentary are three large rectangular pavement teeth ; maxillae with a single series of depressed, conical teeth. Detached teeth are abundant in the Muschelkalk of Southern Germany and France, rare in the Wellendolomite and Alpine Keupeiv Cyamodus, v. Meyer. Skull triangular, snout much compressed. Supra- temporal vacuity elongated oval, nearly three times as large as the orbits, Placodus gigas, Ag. Muschelkalk ; Bayreuth, Germany. A, Palatal, and B, superior aspects of skull, !/3. C, Oral, and D, lateral aspects of man- dible, l/ 3 . Fig. 296. Plaeodw hypsiceps, v. Meyer. Muschelkalk ; Bayreuth, Germany. Lateral aspect of skull, i/ 3 . A, Orbit; A r , External narial opening (after von Meyer). which are placed in anterior third of the skull. Anterior nares small, separate, nearly terminal. On either side of the palate are placed two or three rounded or elliptical-crushing teeth, the hindmost at least twice the size of the anterior. Muschelkalk ; Bavaria. C. rostratus, Miinster sp. ORDER VI CHELONIA 189 Range and Distribution of the Theromorpha. Divisions. Permian. Trias. Europe. N. America. Europe. S. Africa. I. Pareiasaijria. 1. Pareiasauridae . 2. ParioticMdae 3. Diadectidae II. Theriodoxtia. 1. Galesauridae 2. Deuterosauridae 3. Tritylodontidac . III. Axomodontia IV. Placodoktia (Ural ?) Order 6. CHBLONIA. (Testudinata.) 1 Reptiles of stout and wide form of body, encased in a more or less complete bony shell. Quadrate immovably united to the cranial arches. Jaws toothless, I ml covered with horny sheaths ; premaxillae very small, palate completely closed by junction 1 Literature : /.'"///-, G., Osteologische Notizen iiber Reptilien (Zool. Ariz. vol. IX. No. 238), 1886. — Ibid. vol. XI. (1888), pp. 417, 592 ; and vol. XII. (1889), p. 40. — Notes on some little known American fossil Tortoises (Proc. Acad. Nat. Sci. Philadelphia, p. 411), 1891. — Bemerkungen iiber die Phylo- genie der Schildkroten (Anat. Anz. vol. XII. p. 561), 1896. — Boulenger, G. A., Catalogue of Chelonians in the British Museum. London, 1889. — Case, E. C., On the osteology and relationships of Protostega (Journ. Morph. vol. XIV. No. 1), 1897. — Cope, E. D., The Reptiles of the American Eocene (Amer. Nat. vol. XVI. p. 979), 1882.— Ibid, vol. XXX. p. 398, 1896.— Dam's, II".. Die Chelonier der norddeutschen Tertiarformation (Palaeont. Abhandl. Dames und Kayser, vol. VI. . 1894. — Dollo, L., Note sur les Cheloniens de Bernissart (Bull. Mus. Roy. d'Hist. Nat. Belg. vol. J II. p. 63), 1884 ; ibid. vol. IV. (1886), pp. 69, 129 ; and ibid. vol. V. (1888), p. 59.— On the humerus of Euclastes (Geol. Mag. [3], vol. V. No. 6), 1888. — Fraas, E., Proganochelys Quenstedtii Baur (Jahresh. Vereins Naturk. Wiirtb. ), 1899. — Gray, J. E., Notes on the families ami genera of Tortoises (Proc. Zool. Soc. vol. XII. p. 165), 1869. — Hoffmann, C. K., Chelonia, in Bronn's Classen und Ordnungen des Thierreichs, vol. VI. 1879. — Lydekker, R., Siwalik ami Narbada Chelonia (Palaeont. Indica, ser. X. vol. III.), 1886. — Catalogue of the fossil Reptilia ami Amphibia in tin- British Museum, Part III. London, 1889. — Maack, G. A., Die his jetzt bekannten fossilen Schild- kroten, etc. (Palaeontogr. vol. XVIII.), 1869. — Meyer, H. von, Zur Fauna der Vorwelt, Parts 1. and IV. Frankfort, 1845-60. — Owen, li., and Bell, R., Monograph of the fossil Reptilia of the London Clay. Part I. (Palaeont. Soc), 1851. — Owen, R., Monograph of the fossil Chelonian Reptilia, etc., ibid. 185:2-53. — Pictet, F. J., and Humbert, A.. Monographic des Cheloniens de la Molasse Suisse. ( S-eneva, 1856. — Portis, A., Ueber fossile Schildkroten aus dem Kimmeridge von Hanover (Palaeontogr. vol. XXV.), 1878. — Les Cheloniens de la Molasse Vaudoise (Mem. Soc. Palaeont. Suisse, vol. IX. i, 1882. — Reinach, A. v., Schildkrotenreste im Mainzer Tertiarhecken, etc. (Abhandl. Senckenb. naturf. Ges. vol. XXVIII. ), 1900. — Riitimeyer, L., Die fossilen Schildkroten von Soluthurn (Denkschr. Schweiz. naturf. Gesellsch. vol. XXII.), 1867: and ibid. vol. XXV. (1873). — Ueber den Ban von Schale und Schadel bei lebenden und fossilen Schildkroten (Verhandl. naturf. Gesellsch. Basel, vol. III. p. 255), 1872. — Sacco, F., Cheloni Astiani del Piemonte (Mem. Acad. Torino, vol. XX XIX. . 1889. — Wagner, J. A., Schildkroten und Saurier aus den lithographischen Schiefer (Abhandl. bayer. Akad. Wissensch. II. Classe, vol. VII. p. 291), 1853 ; and ibid. vol. IX. (1861), p. §8.— Wielan \ M * M14$^ Q.uJ tin J Fig. 298. Trionyx gangetieus, Cuvier. Recent; India. Superior (.4), and palatal (B) aspects of skull, reduced, bo, Basioccipital ; bsph, Basisphenoid ; ch, Internal nares ; exo, Exoccipital ; fir, Frontal ; j, Jugal ; mx, Maxilla ; N, External nostril ; op, Opisthotic ; pa, Parietal ; pi, Palatine ; pmx, Premaxilla ; prf, Prefrontal + nasal ; pro, Prootic ; ptf, Postfrontal ; q, Quadrate ; qnj, Quadrato-jugal ; S, Supratemporal fossa ; so, Supraoccipital ; sq, Squamosal ; vo, Vomer. are both stout plates, situated in their usual positions. The exoccipital sometimes fuses with the supraoccipital, which is produced beyond a line drawn between the posterior extremities of the squamosal. The foramen magnum is deeper than broad, and bounded by the supraoccipital and the exoccipitals, and occasionally also by the basioccipital. The squamosal joins both the prootic and opisthotic, and is buttressed by the quadrate, which penetrates the otic region by means of a superiorly or inwardly directed process, and is snturally united with the quadrato-jugal. The quadrate sometimes joins both the basisphenoid and basioccipital, but in all Cryptodires it is separated from the basisphenoid by the pterygoids, which form a suture with the basioccipital, or very nearly reach the latter bone, and are in contact with the maxillae (except in the Chelouidae). In none of the Pleurodires do the pterygoids extend posteriorly beyond the quadrate. VOL. II 11>4 liKPTILIA CLASS III The mandibular elements, which are six in number, are so intimately united in the adult as to appear like a single piece. A symphysial suture is present in the Chelydridae, however, at least in young individuals. Teeth are entirely wanting, both on the palate and jaw-bones, but the edges of the latter are covered with sharp, horny sheaths like the beak of a bird. Limb-girdles.— The limb-girdles (Fig. 299) are remarkable for being enclosed within the external shell, but as they precede the development of the anterior and posterior dorsal ribs in the embryonic state, their apparently abnormal position is seen to be a secondary modification. Of the three branches which constitute the pectoral arch, namely, the scapula, precoracoid, and coracoid, the latter is longest in the Chelonidae, the former in all other Cryptodires. The coracoids are long, distally expanded bones, directed backwards and inwards, but not meeting in the median line. The scapula is slender, rod -like, and upwardly directed. Its distal extremity is attached by ligaments or cartilage to the anterior costal bone, and its proximal end is fused with the precoracoid, which corresponds to an elongated acromial process (" proscapula," Baur ; " clavicle," Cuvier, Owen). The latter is directed for- wards and downwards, and expanded distal end is attached by ligaments to the entoplastron. The humerus exhibits a large spherical head, and a more or less strongly curved shaft. The radius and ulna are of about equal length, except in the Chelonidae, where the former is much longer and situated below the ulna. The proximal carpals are commonly four in number, and the distal five; numerous varia- tions, however, are exhibited by the bones of the manus amongst the different families and genera. Five digits are always present, but sometimes not more than three are clawed. In the pelvic arch the long ilium is loosely attached to the sacrum and eighth costal plate in the Cryptodira, to the sacral ribs in the Trionychoidea; but in .ill existing Pleurodira the pelvis is solidly united with the carapace and plastron, and bears no trace of sacral attachment (Fig. 307). The pubis and i -liium of Cryptodires form ;i ventral symphysis, and their symphysial branches Fig. 299. Cistudo lal" rin, Marsili. [C. (Emys) europaea, Schneid.] Recent; Europe. Ventral aspect, the plastron removed to one side, c, Costal plates : co, Coracoid ; e, Entoplastron ; ep, Epiplastron ; ./, Fibula ; fe, Femur : /<. Humerus ; hpp, Hypoplastron ; hyp, Hyoplastron ; jl, [limn ; /'*. Ischium; m, Marginals; //". Nuchal ; 7)//. Pubis; psc, Precoracoid ; py, Suprapygal ; ;•, Radius; se, Scapula; /, Tibia; u, Ulna; xp, Xiphi- plastron. order vi CHELONIA 195 are either widely separated from each other, or in contact and limiting two obturator foramina (Testudinidae). The pubis sends off a more or less developed process, directed forwards and outwards, which may be subcylindrical, rod-like, or flat and expanded distally ; a lateral process is also present, but usually less developed than that of the pubis, on the ischium of all Oyptodires except in the Chelonidae (Boulenger). The femur is a curved cylindrical bone, and the tibia and fibula are subequal in length. An astragalus (formed of the tibiale + intermedium) which is in contact with both tibia and fibula, and a small outer calcaneum (fibulare) constitute the proximal tarsals ; or among the Emyds, these may coalesce in a single piece. A centrale is distinct in the ( Iwlydridae and most Pleurodires ; and except in the Chelonidae, which have four, the distal row of tarsals contains five bones. Habitat and Geological History. — Many of the Chelonia are terrestrial in habit. a greater number are aquatic, and a few are exclusively marine. About 200 recent species are regarded as well established, most of which are limited to the tropics or warm temperate zones. The earliest known fossil remains are from the Upper Keuper of Wurtemberg (Proganochelys, Chelytherium), and are fortunately tolerably well preserved. None have been discovered in Lower Jurassic rocks, but from the Upper Jura of Solothurn, Northern France, Germany, England, and the United States, a number of forms are kn