CHAPTER XVII.

[592]This structure was first demonstrated by Sir Philip Egerton. See Geol. Trans. 2d series, vol. v. p. 187, pl. xiv.[593]Geol. Trans. 2d ser. vol. v. p. 511, pl. xlii.

[592]This structure was first demonstrated by Sir Philip Egerton. See Geol. Trans. 2d series, vol. v. p. 187, pl. xiv.

[593]Geol. Trans. 2d ser. vol. v. p. 511, pl. xlii.

Lign. 214. Paddles of Ichthyosaurus and Plesiosaurus,1/8nat. size.Lias Shale.Lyme Regis.Fig.1.—Left fore-paddle of the Ichthyosaurus.2.—Left fore-paddle of the Plesiosaurus.

The Ichthyosaurus has abdominal ribs (p. 656, note), as in the Crocodile, and it is therefore inferred that, if oviparous, it did not produce ova in such immense numbers as the Batrachians, &c. A specimen found by the late Mr. Channing Pearce renders it probable that the Ichthyosaurus may have been viviparous. A remarkably perfect adult Ichthyosaurus, examined by this gentleman, contained the bones of a fœtus (a few inches long)in the cavity of the pelvis. This specimen is in the collection of Mr. Pearce, at Bath. Remains or traces of the dermal integument have been discovered in some examples from the Lias of Barrow-on-Soar, Lyme Regis, Ilminster, and the neighbourhood of Tewkesbury.[594]

[594]See Mr. Coles’s interesting paper on the Skin of the Ichthyosaurus, in the Quart. Journ. Geol. Soc. vol. ix. p. 79.

Lign. 215. Hinder Paddle of an Ichthyosaurus(1/3nat.): with the impression of its integuments.Lias.Barrow-on-Soar.(From Geol. Trans. 2d ser. vol. vi. pl. xx.)

Integuments of the Paddle.—The importance of carefully examining the surrounding stone before removing vegetable or animal remains from the matrix in which theyare imbedded, and which has so often been insisted upon in the preceding pages, is strikingly exemplified in the highly interesting example of the hinder paddle of an Ichthyosaurus (I. communis) discovered by Sir Philip Egerton.Lign.215is reduced from the exquisite representation of the specimen accompanying the original memoir by Prof. Owen on this fossil, in the Geological Transactions. The specimen consists of the phalangeal bones of a posterior paddle, with the impression of the soft parts or integuments in their natural position;a, marks the termination or distal extremity of the fin, consisting entirely of the softer integuments; these gradually widen and expand to receive the terminal rows of the phalangeal ossicles or bones, markedb. The upper border of this integumentary part of the paddle (c) is formed by a smooth, well-defined line, apparently a mere duplicature of integument. But the lower margin (d) exhibits the impressions of a series of rays, by which the fold of integument was supported; these rays bifurcate as they approach the margin of the fin, and were probably either cartilaginous, or composed of an albuminous horny tissue, like the marginal rays in the fins of Sharks. Dr. Buckland detected remains of the dermal integument of an Ichthyosaurus in a specimen from the Lias at Barrow-on-Soar (Bd.ii. p. 22, pl. x.); and in a fine skeleton with the four paddles (now in the British Museum), which I obtained from that locality, there were decided traces of the carbonized integuments around each paddle, but which were, unfortunately, chiselled away, in developing the bones, before I was aware of their true nature.

In Mr. Coles’s paper, already referred to, the student has an instructive instance of the value of a careful examination of faint or obscure traces of organic matter accompanying these saurian remains, and how such an examination should be made. The Plate illustrative of the Memoir exhibits the minute, hooked, conical bodies, that form the dense felt-likemass which the black film, frequently accompanying these fossil bones, appears to consist of, when seen under the microscope. To what extent this substance entered into the constitution of the integuments, or of the exact relation of these "setiform scales" to the surface or the interior of the skin, our present knowledge does not enable us to judge.

PLESIOSAURUS.

Plesiosaurus.(Bd.pl. xvi.—xix.)—The animals of this genus present in their osteological structure a remarkable deviation from all known recent and fossil reptiles; uniting the characters of the head of a lizard, with the teeth of a crocodile, to a neck of inordinate length, with such modifications of the ribs, the pectoral and pelvic arches, and the paddles, as to justify the graphic simile of Professor Sedgwick, that the Plesiosaurus might be compared to a serpent threaded through the shell of a turtle.

The character which immediately strikes the observer, is the extraordinary length of the neck, and the relative smallness of the head. The neck, which in most animals is formed of but five vertebræ, and in the extremest recent example, the Swan, does not exceed twenty-four, is in the Plesiosaurus composed of from twenty to forty; and, in some species, is four times the length of the head, and equal to the entire length of the body and tail; while the length of the head (inP. dolichodeirus) is less than one-thirteenth of the entire skeleton. The skull resembles that of the crocodile in its general form, but is relatively smaller, and is more related to the lacertian type. The parietal bone is more triquetal than in the crocodiles; but the zygomatic bone is attached to its lower end. The breathing apertures are situated anterior to the orbits, on the highest part of the head. The lower jaw has the usual structure of the Saurians; but the dentary bone is greatly expanded anteriorly, and united in front (seeBd.pl. xix.). The teeth are implanted in separate sockets, as in the crocodile,and there are from thirty to forty on each side the jaws. They are conical, slender, long, pointed, slightly recurved, and longitudinally grooved from the base upwards; having a long round fang. The pulp-cavity is long and single, surrounded by a body of firm dentine, covered on the crown with a layer of enamel, and at the base with cement (Odont.pl. lxxiv.). The dentition in the Plesiosauri differs from that of the Crocodiles, in the successional teeth emerging through distinct apertures on the inner side of the sockets of their predecessors, and not through the pulp-cavity. The vertebræ are relatively longer than in the Ichthyosaurus, and their articular faces are either flat, or slightly excavated towards the periphery, with a gentle convexity in the centre (Foss. Til. For.pl. ix. fig. 4).[595]

[595]For details, see Brit. Assoc. Rep. 1839, p. 50.

The caudal vertebræ have two distinct hæmapophyses, not united into a chevron-bone.

The cervical ribs, or hatchet-bones, are attached by two articular facets to the bodies of the vertebræ, but with a very narrow space between; scarcely large enough even for the passage of the sympathetic nerve; and apparently not sufficient for the vertebral artery.

Thepectoral archis remarkable for the pair of elongated and broad coracoid bones (Bd.pl. xvii. andLign.213); indeed the coracoids attain their maximum of development in the Plesiosaurus. Theribs, which are very numerous, and extend throughout a great portion of the vertebral column, are connected, anteriorly, in the abdominal region, by several slender bones, calledcostal-arcs, consisting of six or seven pieces to each pair of ribs; the Ichthyosaurus has a similar structure, but the arcs are composed of but five pieces. As these connecting bones are so constructed as to admit of a certain degree of gliding motion upon each other, it is inferred that, by this mechanism, considerable expansionof the pulmonary cavities in these air-breathing marine reptiles was obtained (Bd.pl. xviii. fig. 3).

The paddles are composed of fewer and more slender bones than in the Ichthyosaurus, and must have been of a more elegant form, and possessed greater flexibility (Lign.214,fig.2). The wrist (carpus) consists of a double row of round ossicles, which are succeeded by five elongated metacarpal, and these by numerous, slender and slightly-curved phalangeal bones.

Sixteen species of Plesiosaurus and ten of Ichthyosaurus have been discovered in the British strata, and nearly forty are now known; their geological range is from the Lias to the Chalk, inclusive.[596]Their remains are found most abundantly in the Lias and Oolite. I have collected many Plesiosaurian vertebræ in the Wealden, and in the Green Sand of Farringdon. No traces of Ichthyosauri have been observed in the Wealden; but vertebræ, and jaws with teeth, occur in the lower Chalk and Galt of Kent and Cambridgeshire.[597]On the Continent the remains of Enaliosaurians have also been discovered in the same formations.

[596]SeePetrifactions, for an account of the specimens in the British Museum.[597]Brit. Assoc. Trans. 1845, Sect. p. 60. The Enaliosaurian bones and teeth found in the Cretaceous deposits of England have been fully described and illustrated by Prof. Owen, in Dixon’sFossils of Sussex, &c., and in his Monograph on the Fossil Reptiles of the Cretaceous Formation, Palæontographical Society, 1851.

[596]SeePetrifactions, for an account of the specimens in the British Museum.

[597]Brit. Assoc. Trans. 1845, Sect. p. 60. The Enaliosaurian bones and teeth found in the Cretaceous deposits of England have been fully described and illustrated by Prof. Owen, in Dixon’sFossils of Sussex, &c., and in his Monograph on the Fossil Reptiles of the Cretaceous Formation, Palæontographical Society, 1851.

Pliosaurus.—-This name designates a gigantic extinct reptile, of which the upper and lower jaws, with teeth, considerable portions of the vertebral column, and many bones of the extremities have been discovered in the Kimmeridge clay of Oxfordshire, and are preserved in Dr. Buckland’s museum. The teeth resemble those of the Plesiosaurus in their general aspect, being of a conical form, longitudinally grooved, and having a long fang; but they are readily distinguished by the subtrihedral form of the crown, producedby the smooth, flat, or slightly convex external surface; they approach in this respect the tooth of the Mosasaurus; from the latter, however, even fragments may be known by the presence of longitudinal ridges. The animal itself was an enormous marine reptile, allied to the Plesiosaurians, but more nearly related to the Crocodilians.[598]

[598]Brit. Assoc. Rep. 1841, p. 60. Odont. pl. lxviii.

II. Crocodilians.—The loricated, or mailed, Saurian reptiles, viz. the Alligators, Crocodiles, and Gavials, are well known as the largest living forms of cold-blooded oviparous quadrupeds.[599]No relics of any recent species have been observed in a fossil state; except that of the Gangetic Gavial, which has been found fossil in the Sub-Himalayas by Capt. Cantley and Dr. Falconer; but remains of Crocodilians of the existing generic type, having the spinal column composed of concavo-convex vertebra; (i. e. united to each other by a ball and socket-joint), the convexity being behind, or towards the tail, have been found in the London Clay at Hackney and the Isle of Sheppey, and in the eocene deposits on the coast of Western Sussex and Hants.[600]But the Crocodiles of the Wealden, Purbeck, Oolite, and Lias differ materially in their osteological characters from the recent species, particularly in the structure of the vertebral column; which in one genus is composed of concavo-convex vertebra; placed in a reversed position to those of the existing species, the ball or convexity being anterior, or directed forwards. In the othergenera, both the articular faces of the vertebræ are either flat, or concave.[601](Geol. S. E.p. 296.)

[599]A detailed and philosophical examination of the osteology of the recent Crocodilia has lately been given to the scientific world by Prof. Owen, in his Monograph on the Reptilia of the London Clay, published by the Palæontographical Society of London, 1850. A condensed notice, by Prof. Owen, of the dental apparatus of the Crocodilians, is to be found in theCyclop. Anat.Art.Teeth.[600]See Brit. Assoc. Rep. 1844, Sect. p. 50; and 1847, Sect, p. 65.[601]Cuvier, Oss. Foss. tom. v. p. 153; on the fossil Crocodiles of Honfleur, which comprise both the types alluded to in the text.

[600]See Brit. Assoc. Rep. 1844, Sect. p. 50; and 1847, Sect, p. 65.

[601]Cuvier, Oss. Foss. tom. v. p. 153; on the fossil Crocodiles of Honfleur, which comprise both the types alluded to in the text.

Vertebræ of two species of Crocodilians or Alligators have been found in the cretaceous Green Sand of the United States: these are of the true procœlian[602]type, as in the existing species; but they present peculiar characters in the modification of the apophyses.[603]

[602]Procœlian, concave before: amphicœlian, concave at both ends platycœlian, flat in front and concave behind.[603]See Quart. Geol. Journ. vol. v. p. 380, pl. x.

[602]Procœlian, concave before: amphicœlian, concave at both ends platycœlian, flat in front and concave behind.

[603]See Quart. Geol. Journ. vol. v. p. 380, pl. x.

Lign. 216. Skull and Jaws of Teleosaurus.1/8nat.Lias.Whitby.Fig.1.—Upper view of the cranium of Teleosaurus.c, occipital condyle.t,t, temporal fossæ.o,o, orbits.n, nasal apertures.2.—Muzzle or anterior extremity of the jaws ofSteneosaurus.3.—The same of Teleosaurus.4.—Lateral view of the cranium and lower jaw of Teleosaurus.

With this exception, the Crocodilians with broad muzzles, as the Cayman and Alligator, have no representatives below the Tertiary formations; theCrocodiliaof the Secondary deposits being all referable to the division having elongated beaks, like the recent Gavials (Bd.p. 250). The fossil Crocodiles of the latter type are arranged in two genera;namely,Teleosaurus[604](Lign.216,fig.3), in which the nasal apertures terminate in two orifices, (not blended into a single opening as in the recent species,) in front of the nose; andSteneosaurus(Lign.216,fig.2), in which the breathing canals end in two nearly semicircular vertical openings at the extremity of the muzzle. (See alsoBd.pl. xxv.)

[604]The skeleton of a recent Gavial, and that of a Teleosaur, are represented on one plate, for comparison, in Prof. Owen’s Monograph,loc. cit.

The British fossil species, most nearly related to the recent, occur in the Lower and Middle Eocene of the South-East of England. Two fine specimens of the skull ofCrocodilus toliapicus, Cuvier and Owen (C. Spenceriof Dr. Buckland), have been found at Sheppey, as well as a skull ofC. champsoïdes(Owen), and numerous vertebræ referable to each species. The eocene deposits of Hordwell Cliff have yielded theCrocodilus Hastingsiæ,[605]and theAlligatorHantoniensis(Petrif.p. 467; andCharlesworth's Geol. Journ.pl. i.); and the remains of a Gavial (Gavialis Dixoni, Owen, in Dixon’sFoss. Suss.) have been found at Bracklesham.[606]

[605]This fossil Crocodile supplies a good illustration of the biconvex body of the first caudal vertebra already described as peculiar to these loricated reptiles, see page 656; and I have subjoinedLign.217in illustration of this structure.[606]Most of these valuable fossils are in the British Museum. They are all described in detail and most elaborately illustrated in Prof. Owen’s Monograph, already referred to.

[606]Most of these valuable fossils are in the British Museum. They are all described in detail and most elaborately illustrated in Prof. Owen’s Monograph, already referred to.

Lign. 217. First Caudal Vertebra of Crocodilus Hastingsiæ.1/3nat.Eocene.Hordwell Cliff.s, spinous process, or neural spine.z, anterior zygapophysis or oblique process.z1, posterior zygapophysis.d, left diapophysis, or transverse process.a, p, body or centrum, convex at both ends.

In the strata of Tilgate Forest, associated with innumerable remains of reptiles of various kinds, teeth of the Crocodilian type, belonging to two genera, are not uncommon.[607]The first kind (Suchosaurus[608]cultridensof Prof. Owen) is a tooth about an inch in length, of a slender acuminated form, compressed laterally, and gently recurved, with a sharp edge in front and behind; resembling, in its general figure, the tooth of a Megalosaurus, with the serrations on the edges worn off (Pl. VI. fig. 7). The sides of the crown are marked with a few longitudinal grooves. Some biconcave vertebræ found in the same quarries, and characterized by the compressed wedge-shaped form of the centre (Foss. Til. For.pl. ix.fig.11), are supposed by Professor Owen to belong to the same reptile as the teeth above described; but it is hazardous to pronounce on the identity of these detached teeth and bones, without more corroborative proof than has hitherto been obtained.

[607]Foss. South Downs, p. 50.Foss. Tilg. For.p. 64; pl. v. figs. 1-3, 7.Cuv. Oss. Foss.tom. v. p. 161, pl. x. See also Owen's later examination of these remains,Report Brit. Assoc.1811, p. 67; andCyclop. Anat.Art.Teeth.[608]Brit. Assoc. Rep. 1841, p. 68.Sucho-saurusis derived fromSuchus, orSuchis, the name given by Strabo to the sacred crocodile of the Egyptians.

[608]Brit. Assoc. Rep. 1841, p. 68.Sucho-saurusis derived fromSuchus, orSuchis, the name given by Strabo to the sacred crocodile of the Egyptians.

Swanage Crocodile.(Goniopholis crassidens.)Petrif.p. 170,Lign.38.—Under this name, the second species of Crocodilian teeth will be considered; the discovery of a considerable portion of a skeleton of a reptile with teeth of this form (Wond.p. 416), in a quarry near Swanage,having disclosed some of the most important osteological characters of the original. These teeth are distinguished from the former by their cylindrical base, and rounded, obtuse, conical crowns (Petrif.p. 171): they somewhat resemble in form those of the Crocodile, but the crown is strongly marked with numerous, well-defined, longitudinal grooves and ridges; and there is a sharp ridge on the middle of each side. A small specimen, broken off at the base, is representedPl. VI. fig. 5; it shows the smooth cylindrical base of the tooth, which is covered with cement, and the finely striated enamelled crown; some of the teeth are more than two inches in length, and one inch in diameter at the base (Foss. Til For.pl. v. figs. 1, 2). I have found these teeth in numerous localities; they are always well preserved, with the ridges sharp, and have a high polish (Geol. I. Wight, p. 357,Lign.30); a series of successional teeth may often be detected in the pulp-cavity (seeWond.p. 414). The detached teeth, and fragments of dermal bones (Lign.207), which, from their constant occurrence with this species, I had been led to consider as belonging to the same reptile, were the only relics that had come under my observation, until the discovery of the Swanage specimen above mentioned.[609]On the two corresponding slabs containing this fine fossil are imbedded many detached teeth; a portion of the left side of the lower jaw, with two teeth in place; ribs and numerous vertebræ, which are biconcave, and have an irregular medullary cavity in the centre of the body; chevron bones resembling those of the Crocodile; the bones of the pelvic arch, and some of those of the extremities. With these are the remains of the osseous dermal cuirass, consisting of numerous scutes (figured and described p. 657,Lign.207), scattered at random among the other relics of theskeleton; some having the inner, and others the external surface exposed; several of these bones are perfect, and exceed six inches in length, and two and a half in breadth. Numerous scales of a small Ganoid fish (Lepidotus minor), common in the Purbeck strata, are also intermingled with these remains. This reptile is namedGoniopholis crassidens, by Professor Owen.[610]

[609]Now in the British Museum: seePetrif.p. 170. A lithograph of one of the slabs was given in the third edition of the Wonders of Geology, 1839.[610]Gonio-pholis:—angle-scute. Brit. Assoc. Rep. 1841, p. 72. Both the slabs of the Swanage specimen are admirably arranged in the same case in the British Museum, with bones and scutes of this reptile from Tilgate Forest; there can be no doubt that the entire lower jaw of the Swanage reptile might have been obtained if the quarry-men had taken the precaution of examining the adjoining block of stone.

[609]Now in the British Museum: seePetrif.p. 170. A lithograph of one of the slabs was given in the third edition of the Wonders of Geology, 1839.

[610]Gonio-pholis:—angle-scute. Brit. Assoc. Rep. 1841, p. 72. Both the slabs of the Swanage specimen are admirably arranged in the same case in the British Museum, with bones and scutes of this reptile from Tilgate Forest; there can be no doubt that the entire lower jaw of the Swanage reptile might have been obtained if the quarry-men had taken the precaution of examining the adjoining block of stone.

Pœcilopleuron.—The remains of an allied genus of Crocodile, thePœcilopleuron Bucklandi(of Deslongchamps), occur in the Oolite, near Caen, Normandy. This reptile, like the Goniopholis, had biconcave vertebræ, with a large medullary cavity in the middle of the centrum. The body of the vertebræ is contracted in the middle, the neural arch anchylosed, with no trace of suture, and with a thin spinous process, which is remarkable for its backward inclination. Vertebræ of this character also occur in the Wealden strata of Tilgate Forest and the Isle of Wight.[611]

[611]Brit. Assoc. Rep. 1841, p. 84.Foss. Til. For.pl. ix. fig. 8, represents a caudal vertebra.

Teleosaurus.(Bd.pl. xxv.)—In the Oolite of England and the Continent, the remains of a genus of extinct reptiles, having, like the recent Gavial, long slender muzzles, have been discovered in several localities. These fossils consist of the osseous scutes of an imbricated dermal cuirass; of the cranium and jaws with teeth; of the vertebral column; and many other bones. The characters of the dermal scutes, and of the muzzle with its terminal nasal apertures, have already been described (p. 659, andp. 676). There areseveral species ofTeleosaurus; a splendid specimen ofT. Chapmanni, fifteen feet long, from the Lias-shale on the Yorkshire coast, is preserved in the Whitby Museum; and there are interesting examples in the British Museum.[612]Teleosaurian remains have been found in the Oolite at Stonesfield, and at Deddington, Oxfordshire; and Mr. C. Moore, of Ilminster, whose museum is rich with perfect Ichthyosaurs and Fishes from the Upper Lias of the neighbourhood, has been highly successful in developing some charming specimens of small Teleosaurs from out of the same deposit. In the Oolite of Caen, in Normandy, very fine specimens ofT. Cadomensishave been discovered; and from these the illustrious Cuvier first determined the character and affinities of the original.[613]The British Oolite contains also the relics of a reptile with biconcave vertebræ, belonging to the genusSteneosaurus: the cranium with the jaws and teeth have been found in Kimmeridge clay, at Shotover (Bd.pl. xxv.).[614]

[612]Petrifactions, p. 178.[613]Oss. Foss. tom. v. p. 127.[614]Report Brit. Assoc. 1841, p. 82.

[612]Petrifactions, p. 178.

[613]Oss. Foss. tom. v. p. 127.

[614]Report Brit. Assoc. 1841, p. 82.

From the Jura limestone at Monheim, in Franconia, the remains of a small Crocodilian reptile (Teleosaurus priscus), with a long slender muzzle, have been obtained. In a specimen[615]from the former locality, the skull, jaws with teeth, the entire vertebral column, and many parts of the skeleton are preserved: the entire length is but three feet.

[615]Now in the British Museum: seePetrif.p. 178, where a detailed description of this unique fossil is given. See alsoOssem. Foss.tom. v. pl. vi.

Streptospondylus,Lign.206,figs.5, 7.—Baron Cuvier in his celebrated work, "Recherches sur les Ossemens Fossiles," has given an elaborate description of the remains of two kinds of slender-nosed Crocodilians, from the Kimmeridge clay of Honfleur, and the Oxford clay of Havre.

The specimens consist of the jaws with teeth, vertebræ,and some bones of the extremities.[616]In one species, the vertebræ are biconcave; in the other, they are convexo-concave, and present a remarkable deviation from the recent Crocodilian type, namely, that they are placed in a reversed position,—the convex face of the vertebra being directed anteriorly, or towards the cranium, and the concavity posteriorly; the name of the genus,Streptospondylus(reversed-spine), denotes this peculiarity of structure. The bodies of three or four large convexo-concave cervical vertebræ, were discovered in the Tilgate strata many years since, and are described in my various works (Geol. S. E.p. 300); but no suspicion was then entertained of their belonging to this genus, although I had repeatedly compared them with the figures of the Honfleur crocodile,[617]the imperfect state of the processes obscuring their true characters. Professor Owen first detected the true character of these Wealden vertebræ, in a large cervical, six inches long (now in the British Museum), in which two oblique processes are preserved on the concave end of the bone, their flat, oblong, articular faces, are directed downwards and outwards,—a character which at once proves them to be the posterior pair, for the anterior oblique processes would be directed upwards and inwards.[618]Vertebræ of the same species occur in the Wealden of the Isle of Wight; and of another species in the Oolite at Chipping Norton, and in the Lias of Whitby.

[616]Oss. Foss. tom. v. p. 143, pl. viii. ix.[617]Reduced figures of two of these vertebræ are given inLign.206,figs.5 and 7, p. 653.[618]Brit. Assoc. Rep. 1841, p. 92. The position of the articulating surfaces of the oblique processes (zygapophyses) in more perfect specimens, subsequently discovered in various localities of the Wealden, established the existence not only of a saurian allied to the Streptospondylus, but also of other reptiles whose spinal column was wholly or in part made up of vertebræ which were convex in front and concave behind, as in the cervicals and anterior dorsals of certain mammalia. Some of these fossil vertebræ Dr. Melville has referred, with great probability, to the cervical region of the Iguanodon (seePetrif.p. 259); others cannot at present be satisfactorily assigned to any known genus of reptiles.

[616]Oss. Foss. tom. v. p. 143, pl. viii. ix.

[617]Reduced figures of two of these vertebræ are given inLign.206,figs.5 and 7, p. 653.

[618]Brit. Assoc. Rep. 1841, p. 92. The position of the articulating surfaces of the oblique processes (zygapophyses) in more perfect specimens, subsequently discovered in various localities of the Wealden, established the existence not only of a saurian allied to the Streptospondylus, but also of other reptiles whose spinal column was wholly or in part made up of vertebræ which were convex in front and concave behind, as in the cervicals and anterior dorsals of certain mammalia. Some of these fossil vertebræ Dr. Melville has referred, with great probability, to the cervical region of the Iguanodon (seePetrif.p. 259); others cannot at present be satisfactorily assigned to any known genus of reptiles.

A concavo-convex caudal vertebra, with the relations of which I am unacquainted, was found in the same quarry in Tilgate Forest; a reduced outline of this unique fossil is given inLign.206,fig.1. The centrum is of a sub-cylindrical form, and the articular face in front is concave, and that behind, convex; with a chevron-bone that is anchylosed to the body of the vertebra, as in some of the caudals of the Mosasaurus, and terminates in an inferior spine (f.); the pair of anterior oblique processes remains; the neural spinous process is destroyed.

Cetiosaurus.—From a considerable number of vertebæ and bones of the extremities of some gigantic aquatic reptiles, discovered in the Oolite in various places in Oxfordshire, Northamptonshire, and Yorkshire, the present genus was established; the name being intended to indicate a distant general resemblance of these extinct Saurians to the Cetaceans.[619]The vertebra; differ from those of the Iguanodon in having their articular faces of a sub-circular form, and the body relatively short; the anterior face is nearly flat, and the posterior concave, in the dorsal vertebra;; but in the caudal both faces are concave, and have a well-defined elevated margin, which gives the body a deeply excavated character, easily recognizable. Vertebræ of this kind were among my earliest discoveries in the strata of Tilgate Forest. (Geol. S. E.p. 282.) Some specimens are eight inches in the transverse diameter of the articular face, and but four and a half inches in the antero-posterior length of the body.[620]The original animals are supposed to have been of aquatic,and probably of marine habits, on the evidence of the sub-biconcave structure of the vertebræ and of the coarse cancellous tissue of the long bones, which are destitute of a medullary cavity. They must have rivalled the modern whales in bulk, for some specimens indicate a length of forty or fifty feet; they are supposed to have had web-feet, and a broad vertical tail.[621]

[619]Proc. Geol. Soc. vol. iii. p. 457.[620]The osteological characters of these remains, and the physiological relations of the original animals, are described inBrit. Assoc. Rep.1841, pp. 94-102.[621]Brit. Assoc. Rep. 1841, p. 102.

[619]Proc. Geol. Soc. vol. iii. p. 457.

[620]The osteological characters of these remains, and the physiological relations of the original animals, are described inBrit. Assoc. Rep.1841, pp. 94-102.

[621]Brit. Assoc. Rep. 1841, p. 102.

Polyptychodon.[622]—The remains of another gigantic marine Saurian have been discovered in the Green Sand at Hythe, in Kent; they consist chiefly of the bones of the pelvis and hinder extremities.[623]The femur must have been nearly four feet in length. The long bones have a cancellated structure, without a medullary cavity 3 the outer surface is finely striated. Probably in a recent state the cells were filled with oil, as in theCetacea. Neither the vertebræ nor the teeth of this reptile are known; but, provisionally, these remains have been referred to the same animal as that to which the large, conical, longitudinally ridged teeth belonged, which have been found in the Kentish Rag, at Maidstone, and in the Chalk of Sussex, and have been namedPolyptychodon continuus.[624]Teeth ofP. interruptusare not unfrequent in the Cretaceous series; and a portion of the lower jaw of this species, from the Chalk of Kent, is in Mr. Toulmin Smith’s collection.[625]

[622]Poly-ptych-odon; many-wrinkle-tooth.[623]Geol. Proc.vol. iii. p. 449. The bones from Hythe were presented by their discoverer, H. B. Makeson, Esq., to the British Museum. SeePetrifactions, p. 200.[624]Owen’s Monograph, Cretac. Reptilia, Pal. Soc. p. 47.[625]Ibid. p. 55. See also Dixon’s Foss. Suss. p. 378. Teeth of the Polyptychodon are figured inOdontography, pl. lxxii.

[622]Poly-ptych-odon; many-wrinkle-tooth.

[623]Geol. Proc.vol. iii. p. 449. The bones from Hythe were presented by their discoverer, H. B. Makeson, Esq., to the British Museum. SeePetrifactions, p. 200.

[624]Owen’s Monograph, Cretac. Reptilia, Pal. Soc. p. 47.

[625]Ibid. p. 55. See also Dixon’s Foss. Suss. p. 378. Teeth of the Polyptychodon are figured inOdontography, pl. lxxii.

FOSSIL REPTILES; COMPRISING THE DEINOSAURIANS, PTERODACTYLES, TURTLES, SERPENTS, AND BATRACHIANS.

III. Deinosaurians.—The OrderDeinosauria(fearfully-great lizards) has been established for the reception of those extinct colossal reptiles, comprising theMegalosaurus,Hylæosaurus,Iguanodon, andPelorosaurus, which, in their organization, present the transition from the Crocodilians to the Lacertians, and whose essential osteological characters Professor Owen has described as follow:—

"This group, which includes at least three well-established genera of Saurians, is characterized by a large sacrum, composed of five anchylosed vertebræ of unusual construction; by the height, breadth, and outward sculpture of the neural arch of the dorsal vertebræ; by the two-fold articulation of the ribs to the vertebra:, viz. at the anterior part of the spine by a head and tubercle, and along the rest of the trunk by a tubercle attached to the transverse process only; by broad, and sometimes complicated, coracoids, and long and slender clavicles; whereby Crocodilian characters of the vertebral column are combined with a Lacertian type of the pectoral arch. The dental organs also exhibit the same transitional or annectent characters, in a greater or lesser degree. The bones of the extremities are of large proportional size for Saurians; they are provided with large medullary cavities, and with well developed and unusual processes, and are terminated by metacarpal, metatarsal, and phalangeal bones, which, with the exception of the ungual phalanges, more or less resemble those of the heavy pachydermal Mammals, and attest, with the hollow long-bones, the terrestrial habits of the species.

"The combinations of such characters, some, as the sacral ones, altogether peculiar among Reptiles, others borrowed, as it were, from groups now distinct from each other, and all manifested by creatures far surpassing in size the largest of existing reptiles, will, it is presumed, be deemed sufficient ground for establishing a distincttribe or sub-order of Saurian Reptiles, for which I would propose the name of Dinosauria.

"Of this tribe the principal and best established genera are theMegalosaurus, theHylæosaurus, and theIguanodon; the gigantic Crocodile-lizards of the dry land; the peculiarities of the osteological structure of which distinguish them as clearly from the modern terrestrial and amphibious Sauria, as the opposite modifications for an aquatic life characterize the extinctEnaliosauria, or Marine Lizards."[626]

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