Gideon Algernon Mantell

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

III. Deinosaurians.—The Order Deinosauria (fearfully-great lizards) has been established for the reception of those extinct colossal reptiles, comprising the Megalosaurus, HylÆosaurus, Iguanodon, and Pelorosaurus, 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 distinct tribe 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 the Megalosaurus, the HylÆosaurus, and the Iguanodon; 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 extinct Enaliosauria, or Marine Lizards."[626]

[626] Brit. Assoc. Rep. 1841, p. 103.

The elaborate investigation of the fossil remains of these stupendous beings, and the luminous exposition of their organization and physiological relations, embodied in the report to which the above extract is introductory, are among the most important contributions to PalÆontology, and afford a striking example of the successful application of profound anatomical knowledge to the elucidation of the most marvellous epoch in the earth’s physical history, the Age of Reptiles.

From the great size of the bones of these reptiles, their remains have excited the curiosity even of the common observer; and although an exaggerated idea has been generally entertained of the magnitude of the original animals, yet, even when reduced to their natural proportions by the rigorous formula of the anatomist, applied to the accumulated relics which years of laborious research have exhumed from their rocky sepulchres and deposited in our museums, their dimensions are sufficiently stupendous to satisfy the most enthusiastic lover of the marvellous.

Let the reader visit the British Museum,[627] and after examining the largest thigh-bone of the Iguanodon, repair to the zoological gallery, and inspect the recent Crocodilian reptiles, some twenty-five or thirty feet in length; and observe that the fossil bone equals, if not surpasses, in size, the entire thigh of the largest of existing reptiles; then let him imagine this bone clothed with proportionate muscles and integuments, and reflect upon the enormous trunk which such limbs must have been destined to move and to sustain—and he will obtain a just notion of the appalling magnitude of the lizards which inhabited the country of the Iguanodon.

[627] See Fossils of the British Museum, p. 227.

The general characters of the extinct reptiles comprised in the order Deinosauria[628] must be known to the intelligent reader, from the various popular notices which have from time to time appeared; and their names have become as familiar as household words. I shall here restrict myself to a few general remarks on the form and structure of the teeth, and of some of the more important bones of the best known species of these great reptiles.[629]

[628] In the new edition of Pictet’s PalÉontologie (now in course of publication), two 4to. plates (xxiii. and xxiv.) are devoted to the illustration of the remains of these colossal reptiles.[629] For further account of the Iguanodon, see Petrif. p. 224, &c.; of the HylÆosaurus, ibid. p. 314, &c.; of the Pelorosaurus, ibid. p. 330, &c.; of the Regnosaurus, ibid. p. 333, &c.; and of the Megalosaurus, ibid. p. 328, &c.

Lign. 218. Megalosaurus Bucklandi. ¹/₄ nat.
Great Oolite. Stonesfield, Oxfordshire.
Portion of the left ramus of the lower jaw, containing several teeth in different stages of growth: inner aspect.
a, a. Crowns of successional teeth.
b, b. Transverse partitions of the tooth-sockets.

MEGALOSAURUS.

Lign. 219.
Tooth of the Megalosaurus Bucklandi.
(Nat. size.)
Wealden. Tilgate Forest.

Megalosaurus (gigantic lizard) Bucklandi. Lign. 218 and 219. Bd. pl. xxiii. Wond. p 421.—The oolitic flag-stone of Stonesfield, in Oxfordshire, has long been celebrated for the bones and teeth of a gigantic reptile, which Dr. Buckland first described by the name of Megalosaurus, in a highly interesting memoir (Trans. Geol. Soc. sec. ser. vol. i.), illustrated by figures of the teeth in a portion of the lower jaw, the sacrum, femur, and other bones. The remains of this reptile are also frequently discovered in the Wealden (see Foss. Til. For. p. 67, pl. ix. figs. 2, 6). The most important relic of this great carnivorous terrestrial lizard is a portion of the right ramus of the lower jaw, containing one perfect tooth, and the germs of several teeth (Lign. 218). The tooth of the Megalosaurus, (Lign. 219, and Pl. VI. fig. 7,) has a conical, laterally compressed crown, with the point recurved like a sabre, and the edges trenchant and finely serrated. The implantation of the teeth is very peculiar, and exhibits the dentition of the Crocodilians blended with that of the Lacertians. The jaw has an outer parapet, as in the true lizards (see Lign. 205), but the teeth are fixed in distinct sockets, formed by transverse partitions, that are attached to a mesial (inner) parapet, composed of a series of triangular osseous plates; the bases of the old teeth, and the germs of the new ones, being thus enclosed and concealed. The tooth is formed of a central body of dentine, the crown having a coating enamel; and the whole an external investment of cement, which forms a thicker layer around the fang; the pulp-cavity is occupied by coarse bone, in the adult tooth. The microscopical examination shows the dentine to consist of very fine calcigerous tubes, ¹/₂₈₀₀₀th of an inch in diameter, without any admixture of medullary canals, radiating from the pulp-cavity at right angles with the external surface of the tooth, and sending; off numerous secondary branches; these ultimately dilate into, or inosculate with, a stratum of calcigerous cells that separates the dentine from the enamel.[630] A thin slice of a vertical section, viewed by transmitted light, is represented Pl. VI. fig. 7 b; showing the calcigerous tubes radiating from the centre, and terminating in the stratum of cells; this cellular structure is invested with a layer of enamel, and the latter with an external coat of cement, indicated by the dark outline.[631]

[630] Owen’s Odontography, p. 271, which should be consulted for more minute details.[631] To fully comprehend the minute structure of these and the other teeth figured in Pl. VI. Professor Owen’s plates should be examined; the small scale necessarily adopted in the present work rendering it impossible to do justice to the subject.

Four specimens of the sacrum, composed of five anchylosed vertebral (Foss. Til. For. pl. xix. fig. 12), have been discovered; one of these is from Tilgate Forest. The femur of the Megalosaurus has two large rounded trochanters of nearly equal size, below the head of the bone; its shaft is sub-cylindrical, and slightly bowed.

This colossal carnivorous Saurian, whose length is estimated at thirty feet, appears to have been terrestrial, and an inhabitant of the same terra incognita as the Iguanodon; it probably preyed on the smaller reptiles, and the young of the Iguanodon, Crocodilians, &c.

HylÆosaurus (Wealden lizard) Owenii. Wond. pl. iv. and p. 435; Geol. S. E. pl. v.—In the summer of 1832, I obtained the interesting specimen which first demonstrated the existence of the remains of another extraordinary modification of Saurian organization in the Wealden. The circumstances which led to this discovery afford an instructive lesson to the young collector.

Upon visiting a quarry in Tilgate Forest, which had yielded many organic remains, I perceived in some fragments of a large mass of stone, which had recently been broken up and thrown on the road-side, traces of numerous pieces of bone. I therefore collected all the recognisable portions of the block, and had them conveyed to my residence. The first step was to cement together those pieces that would admit of juxtaposition, and these were at length united into a block of stone five feet long, three wide, and about one foot thick. This was firmly fixed in a stout frame, to prevent the separation of the united portions during the process of chiselling. Guided by the indications which the sections visible on the edge afforded, a thin iron wedge was carefully driven in, about half an inch above the uppermost layer of bones, and a large slab was flaked off; the three dermal spines (Wond. pl. iv. 5) in the middle of the specimen were thus exposed, and shivered to pieces; some fragments adhered to the mass broken off, others to the block, and many were detached; every piece, however small, was collected, and those adhering to the slab were chiselled out; and the whole were then carefully replaced and cemented to the bones that remained imbedded in the large block. After an interval of some days, to allow of the firm cohesion of the cemented parts, the task was resumed, and the stone chiselled away, until some portion of the large bones of the pectoral arch (Wond. pl. iv. 7) were observed. The specimen was at length brought to the state in which it now appears (in the British Museum[632]); but during the progress of its development, which occupied many weeks, it was repeatedly necessary to suspend the work, and unite displaced fragments of bone, and resume the task after their consolidation. The plate in the Geol. S. E. conveys a good idea of the original.

[632] See Fossils, Brit. Mus. p. 139, &c.

The specimen consists of a part of the spinal column, composed of seven dorsal and three or four cervical vertebrÆ, almost in their natural juxtaposition, with obscure indications of a part of the base of the skull; eleven ribs; the bones of the pectoral arch (two coracoids and two scapulÆ); with numerous dermal bones and spines. A second specimen of this reptile was found near Bolney, in Sussex; and like the former, it was, unfortunately, almost wholly destroyed by the labourers; but I obtained many bones, some of which are perfect, and indicate an animal of considerable magnitude: a scapula, nineteen inches long, an arm-bone or humerus, numerous ribs, bones of the phalanges, &c. A fine series of twenty-six caudal vertebra, having a total length of nearly six feet, with chevron bones and dermal spines, was discovered in 1837, in Tilgate Forest.[633] A few detached bones are the only other relics of this reptile that have come under my observation.[634] The osteological characters presented by these remains afford another example of tire blending of the Crocodilian with the Lacertian type of structure; for we have in the pectoral arch the scapula or omoplate of a crocodile associated with the coracoid of a lizard. Another remarkable feature in these fossils is the presence of the large angular bones or spines (described p. 660, figured Lign. 208), which, there is reason to infer, constituted a serrated crest along the middle of the back: and the numerous small oval dermal bones, which appear to have been arranged in longitudinal series along each side of the dorsal fringe. (Geol. S. E. p. 323.)

[633] See Fossils, Brit. Mus. p. 323.[634] See "Memoir on the Remains of the Iguanodon, HylÆosaurus, and other Saurian Reptiles," by the Author, in Philosophical Transactions for 1841, Part II.

The vertebrÆ, ribs, and other parts of the skeleton found in these specimens also present modifications of structure of great interest.[635] No specimens of teeth have been found associated with the remains of the HylÆosaurus, in such manner as to afford unequivocal proof of their belonging to that animal. But in the same quarries, teeth, decidedly of the Lacertian structure, are occasionally found, and may with some probability be referred to that reptile. These teeth (see Pl. VI. fig. 6a.) are about 1¹/₄ inch in length, and commence at the base with a cylindrical shank, which gradually enlarges into a crown of an obtuse lanceolate form, convex in front, hollowed behind, and terminating in a rounded obtusely angular apex, the margins of which are generally more or less worn.[636] The crown is solid, but the fang encloses a small pulp-cavity; the surface is enamelled, and covered with very fine longitudinal striÆ; the base in every specimen appears broken transversely, as if it had been anchylosed to the jaw, or to the base of a socket. The fang never presents an appearance of lateral adhesion, as if belonging to a Pleurodont lizard. Sections of these teeth expose a simple, central, medullary canal, the upper part of which is generally filled with the ossified remains of the pulp; and this is surrounded by a body of firm dentine, with extremely minute calcigerous tubes radiating from the centre to the periphery of the tooth, which is invested with a relatively thick coat of enamel, in which no structure is apparent. Pl. VI. fig. 6b represents a small portion of a vertical slice, highly magnified and viewed by transmitted light. The reference of these dental organs to the HylÆosaurus must not, however, be considered as conclusive, until confirmed by the discovery of the teeth attached to the jaw, in connexion with other parts of the skeleton. The locomotive organs of the HylÆosaurus are but imperfectly known; a perfect humerus, one phalangeal bone, and fragments of the fibula (the small bone of the leg) are the only bones hitherto observed. The length of this reptile, which was probably terrestrial and herbivorous, may be estimated at from twenty to thirty feet.

[635] See Report, Brit. Assoc. 1841, pp. 111-120. Phil. Trans. 1841, pp. 141-144, pl. x.[636] Rep. Brit. Assoc. 1841, p. 118. Geol. S. E. England, pl. ii. figs. 2, 4. Phil. Trans. 1841, p. 144, pl. vi. figs. 9, 10, 11.

Iguanodon. Ligns. 219 to 226; Wond. pl. ii. iii., and pp. 422, &c.—Soon after my first discovery of the remains of vertebrated animals in the strata of Tilgate Forest, some teeth of a very remarkable character particularly engaged my attention, from their dissimilarity to any that had previously come under my notice.[637] Attention having been directed to these interesting fossils, examples were soon discovered of teeth in various conditions, from the sharp, unused tooth of the young reptile, to the obtuse, worn-out crown of the adult. From the resemblance of the perfect teeth to those of the Iguana (Lign. 205, p. 649), a land lizard of the West Indies, I proposed the name of Iguanodon (signifying an animal with teeth like those of the Iguana) for the extinct reptile to which they belonged. The numerous bones and teeth subsequently exhumed from the strata of Tilgate Forest and other localities in the Wealden of Sussex and of the Isle of Wight, and the considerable portion of the skeleton of an individual discovered by Mr. Bensted in the Kentish Rag, have supplied the data upon which our present knowledge of the characters of the original is based.

[637] These are described in Foss. South D. 1822, p. 54, under the head "Teeth and bones of unknown animals." This was the earliest published notice of the fossils of the Wealden; it contains also a description of a tooth of the Megalosaurus (p. 55, No. 42).

In Wond, pp. 422-435, a brief account will be found of the character of the teeth, horn, femur, vertebrÆ, &c., and of the Maidstone specimen[638] (Pl. III.).

[638] In a Monograph on the Reptiles of the Cretaceous Deposits of England, published by the PalÆontographical Society, Professor Owen has lately figured anew and described in detail this most valuable fossil skeleton; to which description are appended the Professor’s latest views on the structure of the teeth of this reptile.

The "Geology of the South-east of England" contains accurate figures of the long bones of the leg (Geol. S. E. pl. ii), femur, clavicles (Geol. S. E. pl. iv.), tympanic bone (Geol. S. E. pl. ii.), horn and ungual bone (Geol. S. E. pl. iii.). In the "Fossils of Tilgate Forest," there are fifteen quarto plates devoted to the illustration of the bones and teeth of the Iguanodon and other Wealden reptiles. The osteological structure is fully detailed in Rep. Brit. Assoc. 1841, pp. 120-144. A general notice of the principal bones of the Iguanodon, with plates, will be found in Phil. Trans. 1841, pp. 131-151; and in Petrif. chap. iii. the author has given a detailed account of the most important specimens, both in the British Museum and in his own collection, together with a rÉsumÉ of the palÆontology and geology of the Wealden district.

Lign. 220. Iguanodon Mantelli. ¹/₇ nat. size.
Wealden. Tilgate Forest.
The right ramus of the Dower Jaw; [639] discovered in 1848, by Captain Lambart Brickenden, F.G.S.

Fig.	1.—	The inner aspect, showing three teeth, and the sockets of eighteen. a. Germ of a tooth. b. Perfect crown of a successional tooth. c. Remains of a successional tooth, the upper part having been broken off. d. The symphysial extremity of the jaw. e. The opercular furrow. f. The coronoid process.
	2.—	3, and 4, the teeth a, b, and c, in fig. 1, represented on a larger scale.

[639] For the outer aspect, and a restoration of the whole jaw, Petrif. pp. 247 and 249.

Lign. 221. Lower Tooth of the Iguanodon: nat. size. Wealden.
Tilgate Forest.
The apex slightly worn.

Fig.	1.—	Inner aspect, showing the longitudinal ridges, and denticulated margins of the crown of the tooth.
	2.—	View of the outer surface of the tooth. a. The denticulated margin. b. The apex of the crown, worn by use; b. fig. 2, shows the oblique smooth surface produced by mastication. c. A transverse fracture of the fang, showing a section of the medullary cavity occupied by the ossified remains of the pulp. d. Marks the inferior limit of the denticulated margin; if a line were carried horizontally from d, across the tooth, the under figure would represent a tooth worn flown below the denticulations, and deprived of its peculiar dental characters; in this latter state the tooth somewhat resembles an incisor of a Rhinoceros (see Ligns. 222, 223; and Petrif. Lign. 48).

Lign. 222. Upper Tooth of the Iguanodon: nat. size.
Wealden. Brook Bay, Isle of Wight.
The crown is worn down to an oblique smooth surface, and the fang is absorbed.

Jaw and Teeth of the Iguanodon. Ligns. 219-223.—Although the form and structure of the cranium are unknown, yet the half of a lower jaw, discovered in Sussex by Capt. L. Brickenden,[640] and a fragment of an upper jaw, found some years since,[641] enable us to form a tolerably perfect idea of the structure and functions of the dental organs of the Iguanodon. The unused tooth of this reptile is characterized by the prismatic form of the crown, the presence of from two to four longitudinal ridges on its enamelled face, the denticulated margins (Lign. 221, a), and finely serrated edge of the summit, as seen in Lign. 220, fig. 3. The shank or fang of the tooth (Ligns. 221, 223, fig. 2) is sub-cylindrical, slightly curved, and tapers to a point. The inner surface of the crown in the lower teeth, and the outer surface in the upper, are covered with a thick layer of enamel, but the opposite face of the crown and the sides have but a thin coating of this substance. The teeth of the upper jaw (Lign. 222) are curved in the opposite direction to those of the lower, and have the convexity external, and the concavity internal. Thus the upper and lower molars were related to each other nearly as in the Ruminants; the outer aspect below corresponding to the inner above (see Petrif. Lign. 56, p. 254). The specimens met with have almost always the apex of the crown more or less worn down by use[642] (see Lign. 223), and presenting an oblique, triangular, smooth surface, as in the fine large specimen figured in Lign. 221, which was found imbedded in the trunk of a Clathraria, as if it had snapped off while the animal was in the act of gnawing the tough stem. The denticulated margins are well developed; in fig. 1, they appear as simple serrations; but viewed laterally, they are seen to be formed by a series of denticulated plates (Lign. 223, fig. 6). The crown of a tooth of a young animal, worn at the summit, and presenting but three longitudinal ridges, is represented Pl. VI. fig. 4a. The microscropical structure consists of a simple pulp-cavity in the centre of a body of dentine permeated by calcigerous tubes, but with this peculiar modification, that the dentine is traversed by vascular canals, radiating at definite intervals from the pulp-cavity nearly to the periphery of the tooth, and running parallel with the calcigerous tubes; thus constituting a softer and coarser dentine than in the other reptiles, and resembling that which characterizes the teeth of some of the herbivorous mammals.[643] The crown of the tooth is covered with a layer of enamel, which is thickest on the external surface: and the fang is invested with cement. The structure here described is shown in Pl. VI.; fig. 4b, a vertical, and fig. 4c, a transverse section of a tooth, seen by transmitted light, with a high magnifying power. The calcigerous tubes are ¹/₂₅₀₀₀ an inch in diameter. Sections of the teeth of the Iguanodon are beautiful objects under the microscope, for the medullary canals are generally of a deep yellowish brown colour.

[640] Figured and described in the Phil. Trans. 1848, p. 188, pl. xvi. xvii.[641] Both specimens are fully described in Petrif. pp. 242, et seq.[642] Plates iv. and xvii. in the "Fossils of Tilgate Forest," contain representations of upwards of thirty specimens of teeth in various states of development and detrition.[643] Tomes on the Microscopic Structure of the Tooth of the Iguanodon, Petrif. pp. 239, 240. See also Owen’s Odontography, p. 249, and pl. lxxi.; and Cycl. Anat. Art. Teeth.

Lign. 223. Teeth of Iguanodon. Wealden. Tilgate Forest.

Fig.	1.—	Outer aspect of an upper tooth (in a reversed position), worn flat, and with the fang absorbed; fig. 3, inner aspect of the same tooth. a, a. Flat grinding surface, produced by mastication when all the thickly enamelled portion of the crown is worn away. c. Cavity produced by the pressure of a new tooth.
	2.—	Lower tooth of a young animal, slightly worn: inner aspect.
	4.—	Outer Surface of a lower tooth of an adult; and fig. 5, inner surface of the same. a, a. The hard cutting edge of the oblique surface worn by mastication. c. Indentation produced by the pressure of a successional tooth.
	6.—	Edge view of the serration on fig. 5; magnified.

The dentine is less vascular, and therefore hardest, on that side of the crown which has the thicker coat of enamel; hence the tooth wears away faster on one side than on the other, and an oblique grinding surface, with a sharp edge of enamel, is maintained until the crown is worn away. The internal structure of the teeth of the Iguanodon is thus in perfect accordance with their external configuration, and must have been admirably adapted, in every stage, for the laceration and comminution of the tough vegetable substances which, there is every reason to conclude, constituted the food of this colossal oviparous quadruped.

Vertebra of the Iguanodon,[644] Lign. 206, p. 653; Lign. 224.—The remains of the vertebral column of the Iguanodon, consisting generally of broken and water-worn dorsal and caudal vertebrÆ, deprived of their processes and reduced to the state of the specimens represented Lign. 206, figs. 6 and 8, are so abundant in some of the Wealden strata, that a short account of their characters may be useful. A reference to Lign. 206, and its description, will render the following remarks intelligible to the general reader. The vertebrÆ of the Iguanodon are distinguishable from those of other reptiles which occur in the same strata by the following peculiarities, which the figure of a perfect specimen of a caudal vertebra (Lign. 206, fig. 3) will serve to illustrate. The body, or centrum, is either flat or somewhat depressed on both articular faces; its sides are nearly flat, or somewhat convex, vertically (as in fig 3), and slightly concave lengthwise, or from front to back: in some examples, the body is more contracted towards the inferior surface, as in fig. 6; and in the vertebrÆ, near the middle of the tail, the sides are compressed, so as to give an angular contour and somewhat vertical elongation to the face, as in fig. 4; but in the dorsal vertebrÆ, the articular faces are nearly circular, but somewhat higher than wide. In the caudal vertebrÆ, the inferior angles of the body are truncated (w, figs. 3, 4), and present an oblique, smooth face, to articulate with the chevron bone (fig. 3, f). The annular part is united to the body by suture (fig. 3, o), and anchylosed in the dorsal vertebrÆ; and in these bones the neural arch is very high, and greatly expanded, and its bases extend transversely inwards, and join each other below the spinal canal, forming a ring, or bony channel, to contain the spinal chord.[645] "The transverse processes are straight, and very long in the vertebrÆ from the middle of the trunk, indicating a considerable expanse of the abdominal cavity, adapted for the lodgment of the capacious viscera of a herbivorous quadruped." (Owen.) The spinous processes (Lign. 206, fig. 3, d) are large and of great height in the anterior caudal vertebrÆ, Lign. 224; and here the chevrons, or hÆmapophyses (Lign. 224, b, and Lign. 206, fig. 2, and fig. 3, f), are also of considerable length; the bases of the latter are always united (Lign. 206, fig. 2, g), and often blended, so as to form but one face for articulation with the truncated inferior angles of the body of the vertebra:, leaving a vertically elongated channel for the passage of the large blood-vessels of the tail. The external surface of the vertebrÆ of the Iguanodon is more or less marked with fine longitudinal striÆ; those of the Megalosaurus have a smoother and more polished surface.[646]

[644] A detailed account of the elements of the spinal column of the Iguanodon, and remarks on various fossil vertebrÆ, the relations of which with the Iguanodon have been considered doubtful, will be found in Petrif. pp. 256-279.[645] See also lithographs of dorsal and caudal vertebrÆ from the Kentish Rag; Owen’s Monog. Cret. Rept. (Pal. Soc.) 1851.[646] See Rep. Brit Assoc. 1841, pp. 125-133, where an elaborate investigation of the vertebra: of the Iguanodon is given by Professor Owen.

Lign. 224. Six Caudal Vertebra of the Iguanodon. ¹/₁₄ nat. size.
Wealden. Tilgate Forest.

a, a. Spinous processes (neurapophyses), from 13 to 151/2 inches in height. b, b. Three displaced chevron bones (hÆmapophyses), imbedded in the stone near their original position at the junction of the bodies of the vertebrÆ. c. Anterior articular face of a vertebra.

Bones of the Extremities. Ligns. 225 and 226.—The thigh-bone (femur), both bones of the leg (tibia and fibula), and many of the metatarsal and phalangeal bones have been discovered; the osteology of the hinder extremity is, therefore, almost perfect. The thigh-bone (Lign. 225; and Petrif. p. 292,) is of a very remarkable character, having a closer resemblance to the femur of a huge mammalian, than to that of a reptile.[647] Several perfect specimens have been discovered, as well as the associated bones of the leg (Petrif. p. 293, Lign. 62); but the first fragment that came under my notice, was the middle portion of the shaft of a femur of enormous size, and of an irregular quadrangular form; and so shapeless and unintelligible it then appeared, that several years elapsed before its real nature was determined. (Foss. Tilg. For. pl. xviii.)

[647] See Cuvier’s Ossem. Foss. vol. ii. p. 36.

Lign. 225. Left Femur of the Iguanodon. ¹/₁₀ nat. size.
Anterior aspect.
Wealden. Brook Bay, Isle of Wight.

a. Outer trochanter. b. Median trochanter. c. Inner condyle. d. Outer condyle. e. Anterior infra-condyloid fissure. f. Head of the femur.

An entire thigh-bone of an adult Iguanodon, from the Weald clay in the west of Sussex, measured three feet eight inches in length.[648] end thirty-five inches in circumference at the condyles; and I have a femur of a very young animal, that is but five inches long. The form of the thigh-bone is so peculiar, that fragments may easily be recognised. The head of the femur (Lign. 225, f,) is hemispherical, and projects inwards; there is no appearance of a ligamentum teres; a flattened process or trochanter (Lign. 225, a,) forms the external boundary of the neck of the bone, from which it is separated by a deep and narrow vertical fissure; the shaft is of a sub-quadrangular shape, and a slightly elevated ridge, produced by the union of two broad, flat, longitudinal surfaces, extends down the middle of the anterior face, and, diverging towards the inner condyle, gradually disappears. The bone terminates below in two large condyles, separated in front and behind by a deep, narrow cleft, or groove (Lign. 225, e). Near the middle of the inner edge of the shaft, there is a compressed ridge, with an angular projection, or trochanter. Thus the upper part of the femur maybe known by the presence of the flattened, or laterally compressed trochanter; and if that process be wanting, a fractured surface indicating its position may be detected; the middle of the shaft is characterized by its broad angular faces, and the inner submedian trochanter: the condyloid or inferior extremity of the bone may be distinguished by the deep groove between the condyles, both in front and behind.

[648] The average length of the adult femur is estimated at about four feet five inches.

The arm-bone (humerus) of the Iguanodon has been discovered in the Wealden of the Isle of Wight by Mr. Fowlstone; it is figured and described in Petrif. p. 286. The humerus is also present in the Maidstone specimen[649] of Iguanodon, before referred to at page 692: in pl. ii. of Wond. this bone is termed the radius. The humerus of this reptile is much smaller than the femur; in the Maidstone specimen the former is about 20 inches, and the latter about 33 inches in length.

[649] The two bones marked "6" in pl. ii. Wond. and in Lign. 65, Petrif. (one of which is figured in outline in Lign. 226, fig. 4,) regarded by Prof. Owen as the radius and ulna (the two bones of the fore-arm): the author’s reasons for regarding these bones as metacarpals are given in full at p. 289, Petrif.

As separate bones of the feet of the Iguanodon, for example, metacarpals, metatarsals, phalangeals, and unguals, often occur in the strata of the Wealden, figures of several specimens, on a reduced scale, are introduced in Lign. 226, and may enable the student to identify those he may meet with in his researches.[650] The ungual phalanges, or claw-bones, which were invested with the nail, are sometimes found of an enormous size; from a quarry near Horsham, Mr. Holmes obtained specimens more than five inches long, and three inches wide at the articular extremity.

[650] See Rep. Brit. Assoc. 1841, pp. 137-142.

Length of the Iguanodon.—The length of the united head and trunk, according to my estimate in Geol. S. E. p. 316, is seventeen feet and a half; by Professor Owen’s estimate it is reduced to fifteen feet;[651] a difference of no importance in such merely approximative calculations, particularly when the form of the cranium is unknown.[652]

[651] Ibid. p. 144.[652] The more recently discovered specimen of lower-jaw, already referred to, page 693, indicates a length of between three and four feet for the entire jaw, Petrif. p. 249.

Lign. 226. Bones of the Feet and Claws of the Iguanodon.
Wealden. Tilgate Forest.
(See Wond. pl. in.)

Fig.	1.—	Metatarsal: original 6 inches long: upper surface.
	2.—	Metacarpal bone.
	3.—	Under surface of fig. 1.
	4.—	A phalangeal bone of the fore-foot: the original 14 inches long.
	4a.—	A transverse section of the same, showing the medullary cavity.
	5.—	One of the second row of phalangeal bones of the fore-foot.
	6.—	View from above of one of the claw-bones of the hind-foot; 1/6 nat.
	7.—	Profile of claw-bone of fore-foot:[653] 1/6 nat.
	8.—	Metatarsal, or bone of the hind-foot: 1/8 nat. a. Denotes the proximal articulation, or that nearest the trunk. b. The distal, or extremity most distant from the trunk.

[653] This bone is conjecturally referred by Prof. Owen to the Megalosaurus.

The estimated extent of the tail has been subject to variation. My early estimate of its length gave rise to the idea of this reptile having attained seventy feet in length. Professor Owen, however, considered that the abbreviated character of the anterior caudal vertebrÆ indicated a far less extent of tail, which the Professor estimated at thirteen feet; this opinion, from the evidence then before us, seemed well founded, but from evidence since afforded by a series of eleven caudal vertebra, belonging to the middle region of the tail, that have been lately discovered, (Petrif. p. 312,) it is not at all improbable, that, instead of all the caudal vertebrÆ being abbreviated, these elements of the tail were elongated as in the corresponding part of the skeleton of the Iguana, and that the largest Iguanodons may have attained a length of from sixty to seventy feet.

The author’s physiological inferences as to the structure and economy of the Iguanodon, deduced from the study of the osseous remains of this singular creature, especially the lately discovered remains of the jaw-bones, are given in full at pp. 307-313 Petrif. or Foss. Brit. Mus.: and at pp. 335-338, ibid. may be found some general remarks on the physical geography and the nature of the fauna and flora of the country inhabited by these stupendous reptiles, whose remains are so characteristic of the Wealden rocks.

Jaw of the Regnosaurus. (Petrif. p. 333.)—A portion of the right ramus, or side, of the lower jaw of this reptile was discovered in a block of sandstone from Tilgate Forest. It consists of a fragment, six inches long, of the dentary bones, with a small portion of the opercular; and it contains the fangs of fifteen teeth, which are closely and evenly set in a regular series, and imbedded laterally in grooves, or sockets, in the dentary bone; there are three or four sockets of successional teeth on the inner side of the bases of the old teeth. (Phil. Trans. 1841, pl. v. figs. 1, 2.) Unfortunately, all the crowns of the teeth are wanting. The outer parapet of the dentary piece is entire, and its upper margin is finely crenated. All the fangs of the teeth are exposed, but there are traces of a thin inner wall, indicating the probability that, as in the Megalosaurus, the teeth were supported medially by an osseous plate, and were implanted in distinct sockets.[654] In my memoir on this fossil jaw in the Phil. Trans. (1841, p. 131), I referred it to the genus Iguanodon; but subsequent observations have led me to conclude that it is generically distinct; and in my Memoir on the Jaw of the Iguanodon, in Phil. Trans. 1848 (p. 183), I have proposed for the animal to which it belonged the distinct generic appellation, Regnosaurus, with the specific name Northamptoni.

IV. Lacertian Reptiles.—The recent Lacertians, or true Lizards, are smaller and less highly organized reptiles than the Saurians of the Crocodilian order; and their dermal covering consists of a finer and more delicate squamous integument. They are also characterized by important modification in their osteological structure. The spinal column is almost always composed of concavo-convex vertebrÆ, with the convexity behind; the ribs are slender and rounded, having a single convex tubercle of attachment. The fossil species are, for the most part, of gigantic dimensions, and deviate in a striking manner from any that now exist. VertebrÆ of the recent lacertian type are very rare in the secondary strata; I believe a few in my cabinet, obtained from the sandstone of Tilgate Forest, and which belonged to a very small unknown reptile, are the most ancient examples at present known.

Mosasaurus. Bd. pl. xx.; Wond. p. 311; Petrif. p. 193.—Of the fossil lizard of Maestricht, named Mosasaurus (lizard of the Meuse) from the river adjacent to the quarries of St. Peter’s Mountain, in which its remains have been discovered, I have given a detailed account at pages 193-196 of Petrif. A specimen, with the jaws, and bones of the palate armed with teeth, now in the museum at Paris, has long been celebrated, and is still the most precious relic of this extinct reptile hitherto discovered; a reduced representation is given in Lign. 227; and Pict. Atlas, pl. lxx. This is the Mosasaurus Hoffmanni.[655] The specimen is four and a half feet long, and two and a half feet wide; it consists of both sides of the lower jaw, with the right ramus of the upper jaw in its natural position, and the left, which is displaced, lying across the articular extremity of the left branch of the lower jaw: of the pterygoid bones, which are armed with teeth; of the left tympanic bone (os quadratum), which is but little removed from its natural situation, and connects the lower jaw with the cranium; one of the metacarpal or metatarsal bones, and some fragments.[656]

The teeth are large, and supported on expanded conical osseous eminences, which are anchylosed to the alveolar ridge of the jaw (acrodont). The crown of the tooth is conical and recurved, with the outer face nearly flat, and this space is bordered on each side by a longitudinal ridge; giving the tooth somewhat of a pyramidal figure. (See Ligns. 228-230.) Professor Owen states that the crown consists of a body of simple and firm dentine, with fine and close-set calcigerous tubes, enclosing a simple pulp-cavity; irregular processes of the latter extend as medullary canals into the conical base of the tooth, but not, as in the Iguanodon, into the substance of the coronal dentine; the dentine is invested with a moderately thick coat of enamel.[658]

The vertebrÆ of the Mosasaur, as is usual in the existing lizards and crocodiles, are concave in front and convex behind, and the neural arch is united to the centrum by suture. The entire vertebral column of M. Hoffmanni appears to have consisted of 131 vertebrÆ, of which 97 belonged to the tail.[659] This Mosasaur was about twenty-five feet long.

This extinct lacertian reptile forms an intermediate link between the Saurians without pterygoid teeth (Monitors) and those with them (Iguanas). Its crocodilian affinities are but partial.

The Mosasaurus appears to have had webbed feet, adapted or crawling on land as well as for swimming,[660] and a long and vertically expanded tail, serving as a powerful oar, and enabling the animal to stem the roughest waters.

Prof. Goldfuss has described the remains of another and smaller species of Mosasaurus (M. Maximiliani), from Upper Missouri, U.S.; and Prof. Owen, in Dixon's "Fossils of Sussex," has established a third and still smaller species (M. gracilis),[661] to which he refers the four or five mosasaurian vertebrÆ found in the Chalk of Sussex. Two of these (caudal) are figured in Geol. S. E. p. 146, and Petrif. Lign. 44; and these and others are lithographed in plate viii. of Prof. Owen’s Monog. Cret. Reptilia, 1851.

The remains of Mosasaurus occur also in the cretaceous sands of New Jersey, U. S. (See Dr. Morton’s Synopsis of the Organic Remains of the United States, 1834; and the Quart. Journ. of the Geological Society, vol. v. 1849.)

Leiodon anceps.[662]—Under this name Professor Owen has described a splendid fossil, consisting of a portion of the lower jaw of an acrodont reptile, with teeth, obtained by Edward Charlesworth, Esq. from the Chalk north of the Thames. This specimen was submitted to my inspection, many years since, by Mr. Charlesworth, and I then pointed out the analogy of this acrodont jaw to that of the Mosasaurus.

Prof. Owen in 1840 (Odontog. p. 261), and in 1841 (Rep. Brit. Assoc. p. 144), described and figured some teeth from the same specimen, which were lent by Mr. Charlesworth. These teeth the Hunterian Professor regarded as characteristic of a new genus of Mosasauroid reptile, to which he gave the name Leiodon (in allusion to the smoothness of the teeth). In 1845 (Rep. Brit. Assoc. p. 60) Mr. Charlesworth noticed, and in 1846 (London Geol. Journal, p. 23, plates iv. and vi.) figured and described, the above mentioned portion of jaw with teeth, under the name Mosasaurus stenodon; and in 1851 Prof. Owen figured and described this specimen under the name of Leiodon anceps, which was originally proposed for the animal, as known from its teeth, in 1840.

The portion of bone on which the teeth, five in number are implanted is seven inches in length, and is, in Professor Owen s opinion, the dentary piece of the lower jaw, and not a portion of a pterygoid bone. Mr. Charlesworth has had a section made of four of the teeth, and finds that the pulp-cavities are more or less occupied with solid cones of silex, which must have permeated the osseous parietes of the teeth.

The teeth of Leiodon have a simple pulp-cavity, surrounded by fine dentine, with an external layer of smooth enamel. The apex of the crown is sharp-pointed; the body of the crown is slightly recurved; its base is expanded into a thick circular fang, which is anchylosed to a short conical process of the alveolar border of the jaw: the teeth differ from those of the Mosasaurus in having the outer side as convex as the inner side, the transverse section being an ellipse with pointed ends, which latter correspond with the lateral trenchant edges of the crown of the tooth: the teeth are more closely set than in the Mosasaur and Geosaur. (Owen.)

Geosaurus Soemmeringii. Petrif. p. 175.—In the British Museum are the remains of a reptile from the "white Jura" (upper oolite) of Monheim, in Franconia, which Cuvier describes as being more nearly related to the Lizards than Crocodiles. The length of this reptile is estimated at about ten feet. The eyes had a circle of osseous plates in the sclerotica, like those of the Ichthyosaurus; the teeth resemble those of the Mosasaurus in being sub-compressed and recurved, but they are at once distinguished by their anterior and posterior finely serrated sharp edges; the crown is invested with an external coat of enamel.[663]

Raphiosaurus subulidens.—A portion of a lower jaw, containing twenty-two closely set, subulate teeth, anchylosed by their bases to a shallow alveolar groove and an outer alveolar parapet of bone, as in the Iguana, thus corresponding with the pleurodont Lizards, is described under this name by Professor Owen, (Geol. Trans. 2d ser. vol. vi. pl. xxxix.); and Monog. Cret. Rept. (Pal. Soc.) 1851, p. 19, pl. x. figs. 5, 6. It is from the Lower Chalk, near Cambridge, and is in the collection of James Carter, Esq. of that place. Remains of Raphiosaurus have been found also in the Chalk at Northfleet, Kent.

Dolichosaurus longicollis.—In the Chalk of Kent was found, some years since, a considerable portion of the skeleton of a lacertian reptile, consisting of the posterior half of the spinal column, with remains of the pelvic and thigh bones; it was figured in the Geol. Trans. 2d ser. vol. vi. pl. xxxix.; and is now in the collection of Sir P. G. Egerton. From the researches of the late Mr. Dixon, it appears that a mutilated reptilian head and anterior portion of a spinal column, with fore-arm and scapular bones, now in the collection of Mr. Smith, of Tunbridge Wells, belong to the same skeleton as the vertebral remains above mentioned. Both specimens were obtained at the same time from the well-known chalk-pit at Burham, Kent. Professor Owen has lately described these interesting remains in detail (Monog. Cret. Rept. 1851, pp. 22, &c.), and finds no intrinsic contradiction to exist to the historical evidence adduced as to the probability of the two moieties having belonged to the same individual. In the two specimens there exist sixty-three concavo-convex (procoelian) vertebrÆ, of which fifty-seven form the series between the skull and the pelvis, giving the trunk a length of about eighteen inches. This unique reptile was elongate and snake-like in its form, with the abdomen deep and narrow, like that of the water-snakes: its limbs were short; its tail, from the character of the few caudal vertebrÆ remaining, must have been relatively long and powerful. This long and slender lacertian was therefore probably to a considerable degree aquatic in its habits, swimming with an undulatory eel-like movement.

The Dolichosaurus (long-lizard) presents somewhat of the ophidian character in the number and size of its cervical vertebrÆ, in the size and shape of its ribs, and in the slender proportions of its trunk and head; but, with these partial exceptions, its affinities are truly lacertian. (Owen.)

Rhynchosaurus articeps. Lign. 231.—In a quarry of Upper New Red Sandstone at Grinsell, near Shrewsbury, Dr. O. Ward discovered a skull (3¹/₂ inches long), vertebrÆ, ribs, bones of the pectoral and pelvic arches, portions of two femora with medullary cavities, and fragments of other bones of a very remarkable lacertian reptile (Lign. 231). The lower jaw is preserved with the skull in its natural position. The cranium in its general aspect resembles that of a turtle, rather than of a lizard; for the intermaxillary bones are double, as in Chelonians, and symmetrical, and are not united by a median process; they are very long, and curve downwards, giving the fore part of the skull the profile of a parrot. See Lign. 231.

There are no teeth apparent in either jaw: the margin of the upper maxillary has feeble dentations, but in the lower jaw even these indications are wanting, and it is probable that this reptile had its jaws encased by a bony or horny sheath, as in birds and turtles.[664] (Owen.)

Thecodontosaurus and PalÆosaurus. Ly. p. 306, figs. 348, 349.—Numerous bones and teeth of reptiles occur in the Magnesian Conglomerate, near Bristol, and have been described by Dr. Riley and Mr. Stutchbury in an interesting memoir to which reference should be made for details (Geol. Trans. 2d ser. vol. v. p. 349, pl. xxix. xxx.). The bones denote an approach to the lizards; the teeth are implanted in sockets; these reptiles, therefore, belonged to the group termed thecodont, and the name Thecodontosaurus, given to these extinct Saurians by Dr. Riley, has reference to this character. The teeth are pointed, compressed laterally, slightly convex on each side, with a trenchant, finely serrated edge in front and behind; the fang is sub-cylindrical. Other teeth from the same deposit, possessing the same general characters, but distinguished by peculiarities of form, have been referred to another genus, named PalÆosaurus. The vertebrÆ found associated with the teeth and jaws are biconcave, and are remarkably characterized by the great depth of the spinal canal in the middle of the centrum or body of the vertebrÆ, so that the spinal chord must have presented a moniliform or bead-like appearance. These reptiles, in their thecodont type of dentition, biconcave vertebrÆ, double-headed ribs, and proportionate size of the bones of the extremities, are nearly allied to the Teleosaurus, (see ante, p. 679); but they combine a lacertian form of tooth, and a lacertian structure of the pectoral, and probably of the pelvic arches, with these crocodilian characters; they have also distinctive modifications: such, for example, as the moniliform spinal chord.[665]

Dicynodon. Ligns. 232, 233, 234.—This singular fossil reptile was discovered, by Mr. Bain, in South Africa. It is distinguished, by some remarkable peculiarities of structure, from other animals of the Saurian order; of which it represents a new tribe, or sub-order. The cranium is narrow; the nostrils are divided, as in Lizards, and not confluent, as in Chelonia; the skull, in other respects, much resembles in general appearance that of a Turtle; the orbits are large; the jaws are edentulous, as in the Turtles, with the exception of a pair of long tusks,[666] implanted in sockets in the upper maxillary bone, like those of the Walrus; these tusks are of a finer texture than that of the Crocodile’s teeth, and almost as dense as in the HyÆna. These creatures present in the most striking manner that blending of the peculiarities of several existing orders, which is continually presented to the palÆontologist; for with a type essentially lacertian are combined crocodilian and chelonian modifications. Although no vestiges of these reptiles have been discovered in England or in Europe, yet the occurrence of an allied form, the Rhynchosaurus (Lign. 231), in our New Red Sandstone, and the probability that the South African reptiliferous deposits may, from their position, belong to the Triassic Epoch, induce me to give a somewhat extended notice of these extraordinary fossils: and I am led to do so on another account, namely, because the memoir,[667] of which the following is a brief abstract, is so excellent an example of the manner in which such investigations should be conducted, so as to arrive at any satisfactory conclusions as to the characters and relations of the lost types of beings, whose fragmentary and petrified relics are the only vestiges that remain.

The fossils under consideration were exhumed some years since by Mr. Andrew Geddes Bain, from the intensely hard argillo-calcareous nodules of the sandstone strata which range over an immense tract of country beyond the mountains north of Capetown,[668] The extensive series of these and other fossils from South Africa, collected by the indefatigable labour of Mr. Bain, have lately been deposited in the British Museum; but the specimens described and figured in Prof. Owen’s Memoir, above alluded to, are nearly all that have as yet been successfully worked out from the exceedingly hard matrix in which the bones are imbedded. These consist of crania and jaws, referable to four species.[669]

The most striking character in these crania is the presence of a pair of long, sharp-pointed, gently curved tusks, implanted in the superior maxillary bones, and which descend, one on each side of the fore-part of the lower jaw, as seen in Ligns. 232 and 233, t, t'. This is a dental character which, with this exception, is peculiar to the mammalia (the Walrus, Musk-deer, and Machairodus), and is rare even in that class.

Examination of the skull.—One of the crania showed the median undivided process of a single intermaxillary bone, ascending and separating two distinct anterior nasal apertures; in another, the boundaries of a very much contracted cranial cavity were evident: these characters combined to prove that the skulls were referable to air-breathing oviparous and cold-blooded animals, or Reptiles; but neither to Crocodilians nor Chelonians, and for the following reasons:—

1stly. The originals were not mammalians; for no mammalian has the intermaxillary bone single (as in Lign. 233, a), or the external bony nasal aperture double; and neither mammalian nor bird has the cavity for the brain so relatively small as in this fossil.

2dly. They were not Crocodiles; for in all crocodiles the intermaxillary bone is divided by a suture, and the anterior nasal aperture is single and on the median line, as in mammalia.

3dly. They were not Chelonians; for all turtles have the nasal opening single and placed in the middle of the fore-part of the skull, in the very situation which, in the Dicynodon, is occupied by the convex imperforate median plate of the broad intermaxillary bone.

4thly. They could not be Fishes, as those animals have no well-defined external respiratory nasal apertures.

5thly. They were neither Batrachians (frogs) nor Ophidians (serpents); for, although the reptiles of these two orders have a single intermaxillary and double nostrils, like the fossils, the latter are at once separated from them by the presence of a strong and complete zygomatic arch (Ligns. 232 and 233, g, d), continued from the tympanic bone to the large immovably articulated superior maxillary.

Lastly, the characters last named, and the presence of vertical tympanic pedicles (Lign. 232, l), suspended by their upper part to the junction of the zygomatic and mastoid bones, prove the affinity to the lacertians or true lizards.

These bidental crania have certain characters in common with that of the Rhynchosaur, which is also, as we have before seen, of the true lacertian group, but the Dicynodonts are more nearly allied to the Crocodiles and the Chelonians than the Rhynchosaurus appears to be.

Referring to the original Memoir for anatomical details, I must limit this notice to a few additional general remarks. Both the jaws are edentulous, with the exception of the pair of tusks, as in Chelonians; there are no traces of teeth, or of their sockets, in the lower jaw, which is short and very deep, and anchylosed at the symphysis, as in turtles; the alveolar border forms a smooth trenchant edge, which shuts within the corresponding part of the upper jaw: it is probable that both jaws were covered by horn, as in the chelonians. The tusks are implanted in wide and deep conical alveoli in the suborbital part of the maxillary bone, and project about two inches beyond the sockets (Lign. 232); they are long and pointed, and are directed downwards and forwards, with a slight backward curve, and slightly converge towards their extreme points (Lign. 233). These teeth consist of a simple body of unvascular dentine, with a very thin external coat of enamel. The tooth-ivory is more dense than in any known reptile, and approaches in its intimate texture that of the canines of the carnivorous mammals. The base of the tooth has a conical cavity (Lign. 234), indicating a persistent matrix or dental pulp, the rest of the tooth without the socket being solid. There are no traces whatever of the germs of successional teeth. It is therefore inferred, that, like the tusks and scalpriform incisors of mammalia, the canine or maxillary teeth of the Dicynodon were capable of constant growth and renovation; thus offering an approach to the typical dentition of mammalia, unknown in any other reptiles.

As the points of the teeth in the only known perfect specimen are unworn, it is inferred that these tusks were not employed either as instruments for obtaining food, as in the Dugong, or for locomotion, as in the Walrus, but were simply offensive and defensive weapons.[670]

A few sub-biconcave vertebrÆ and other undetermined bones were associated with these remains; and many similar crania, both with and without the tusks, and other cranial remains with jaws armed with numerous teeth, as well as indications of smaller reptiles, form part of Mr. Bain’s collections now in the National Museum, awaiting the skilful manipulation of the experienced workman to clear away their hard investing matrix, and the scientific examination of the palÆontologist to elucidate their zoological characters.

Telerpeton Elginense (Mantell). Ligns. 235 and 236.—This is the oldest Reptile yet known.[671] Its remains consist of the impression[672] of a skeleton of a small, four-footed, vertebrate animal, on a block of the Old Red or Devonian Sandstone from Spynie, near Elgin, North Britain. It was obtained by Mr. Patrick Duff, in 1851; and a detailed description of this unique fossil, with an illustrative plate, will be found in the Quarterly Journal of the Geological Society, vol. viii. pp. 100, et seq.; together with a notice by Captain Brickenden of the geology of the district where the specimen was found, and a paper on some fossil foot-prints,[673] discovered by this geologist in the same rock.

By reference to Lign. 235, it will be seen that the cranium is almost wholly lost; a few conical teeth, mostly of a very small size, were observed in connexion with the vestige of the jaws. The spinal column is represented by the impressions of about thirty-six vertebrÆ, eleven or twelve of which belong to its caudal portion. The vertebrÆ present some faint evidence of their possessing a biconcave form; the length of one of the dorsal vertebrÆ is ¹/₉th of an inch. There are twenty-one pairs of long slender ribs. The pectoral arch and anterior extremities have nearly disappeared in the fracture of the stone. The pelvis and sacrum are very obscure; the latter is formed probably of two anchylosed vertebra;. The thigh-bones are somewhat curved; the tibia is gently bowed, and expanded at each extremity. There are no remains of the feet.

The structure of this reptilian skeleton, as far as the specimen can serve to show, indicates a peculiar type of organization, in which, as in numerous other extinct forms, in this, as in other Classes, osteological characters are associated which in existing oviparous quadrupeds are restricted to distinct orders and genera.

The lacertian affinities of the Telerpeton are well marked in the relative size and form of the bones of its extremities, the situation of its pelvis, and probably in the articulation and the length of its ribs; but the contracted, biconcave centrum, and the short neural spine of the vertebrÆ, as well as the horizontality of the articulating surfaces of the zygapophyses, and the general uniformity of character throughout the spinal column, are to be regarded as batrachian modifications. Probably the original was a peculiar type, which, in the present state of our knowledge, it would be rash to ascribe to either order. The length of the original animal could not have exceeded six or seven inches. Lign. 236 represents in outline the probable form of this small, but most interesting reptile.

V. Pterosaurians, or Flying Reptiles.—Pterodactylus (wing-fingered reptile). Lign. 237. Petrif. p. 187; Wond. p. 577; Bd. pl. xxi. xxii.—The extinct reptiles denominated Pterodactyles, constituting a few genera of an order of Saurians organized for aËrial life,[674] are unquestionably the most marvellous even of the wonderful beings which the relics of the Age of Reptiles have enabled the palÆontologist to reconstruct. With a long-snouted head and long neck, much resembling that of a bird, bat-like wings, and a small trunk and tail, with lacertian affinities in its skull, teeth, and skeleton, and with a bird-like structure of sternum and scapular arch, these creatures present an anomaly of structure as unlike their fossil contemporaries, as is the duck-billed Ornithorhynchus, of Australia, to existing animals. The cranium, or brain-case, is small; the jaws are either long, and armed with numerous sharp-pointed teeth, or toothless, like those of a bird. The teeth of the Pterodactyle are all laniary; they are simple, of a conical form, recurved, with but little difference in their form and size, and implanted in distinct sockets, with wide intervals between each. In some species there are twenty-eight or thirty in the lower, and twenty-two in the upper jaw.

The orbit is very large; the sclerotica consists of an annular row of bony plates, but less in number than in the Ichthyosaurus; the external orifice of the nostrils is near the orbits; remains of the os hyoides (bone of the tongue) have been observed.

The cervical vertebrÆ are large and strong, and capable of great flexibility forwards and backwards, probably to allow the head to fall back to the centre of gravity during flight. There are frequently traces of ossified condition of the tendons of the muscles of the neck. This is well seen in P. macronyx and P. crassirostris (Lign. 237), and is a peculiarity dependent on the additional support required by the long neck of the animal.

The dorsal vertebrÆ are from seventeen to twenty in number. The sacrum is formed by the coalescence of two vertebrÆ only, as in existing reptiles, and not of many, as in birds and certain extinct saurians. The tail is generally short, an unusual character with saurians; but a species with a long tail occurs at Solenhofen.

There are five toes or digits on each foot; the outer finger of the fore-arm is immensely elongated, for the support of a membranous expansion (the impression of this wing-membrane is preserved on the stone in some examples); and the other digits, of fore and hind feet, terminated in long curved claws. The size and form of the extremities show that the Pterodactylus was capable of perching on trees, of hanging against perpendicular surfaces, and of standing firmly on the ground, when, with its wings folded, it might crawl on all-fours, and walk or hop like a bird. A reference to the graphic description of the characters and probable habits of these beings, by Dr. Buckland, Bd. i. p. 221, and the beautiful illustrations accompanying it (Bd. ii. pl. xxi. xxii.), will equally instruct and gratify the reader.

The most perfect examples of the Pterodactyles have been discovered in the lithographic stone of Monheim, Pappenheim, and Solenhofen, where their bones are associated with the remains of Dragon-flies (see p. 551) and other insects. In England, bones of these reptiles have been obtained from the Lias of Lyme Regis, from the Oolitic slate of Stonesfield, from the Wealden strata of Tilgate Forest, and the Chalk of Kent.[675] One of the most interesting British specimens consists of a considerable part of the skeleton of a species about the size of a Raven, discovered by the late Mary Anning, in the Lias of Lyme Regis, and now deposited in the British Museum.[676] It consists of the principal bones of the extremities, and of several vertebra:, and is figured and described by Dr. Buckland, Geol. Trans. 2d ser. vol. iii. pl. xxvii. This specimen is distinguished by a greater length of the claws (whence the name of the species, P. macronyx, long-claw,) than in any previously known.

The remains of the Pterodactyles of the Chalk, for the most part, indicate a large size for the original animals. It has been estimated that some of these gigantic flying reptiles possessed an extent of wing surpassing that of the great albatross. The Pterodactylus Cuvieri had probably an expanse of wing not less than eighteen feet from tip to tip; another Chalk species, P. compressirostris, fifteen feet; whilst the P. macronyx, of the Lias, measured about four feet seven inches from the extremity of one wing to that of the other.[677]

VI. Chelonian Reptiles.—Those singular reptiles, commonly known by the name of Tortoises and Turtles, and designated by naturalists Chelonia (from Chelone, the Greek term for a Tortoise), are distinguished from all other animals by the osseous cuirass in which their bodies are enclosed, the head and neck, extremities, and tail, alone being excluded. This remarkable bony case is produced by the extraordinary development of the bones of the thorax and back; and consists of an under (sternal) and an upper (dorsal) portion. The breast-plate, or plastron, which is the true sternum, is composed of nine pieces of bone, eight of which are in pairs, and the ninth, or odd plate, is situated between the four anterior plates. The variation in the form of these plates is considerable, and affords important distinctive characters. In the young state of land and fresh-water tortoises, there are vacancies between the pieces, which are filled up in the adult, the whole being ultimately united into one bony plate; but in the marine turtles (and also in the Trionyces, or soft tortoises), these pieces do not completely unite, and interspaces always remain. The bones of which the dorsal buckler, carapace, or upper shield is composed consist of eight of the ten pairs of ribs, united by a longitudinal series of angular plates, which are attached to the annular part of the vertebra throughout the whole, or a great part of their length, according to the age and species of the individual.[678] Numerous modifications exist in the form of the buckler, in its flatness or convexity, in the degree of extension of the ribs, and their angular plates, and in the characters of the scutes or horny integument with which the carapace is covered; and with corresponding variations in the head, and in the locomotive extremities, in the numerous species and genera of the Chelonian reptiles, according to their adaptation to a terrestrial, fluviatile, or marine existence.

The animals of this order are arranged in four principal groups, viz. the marine, or Turtles (Chelones); the fluviatile, or river-Tortoises (Trionyces); the marsh-Tortoises (Emydes); and the terrestrial or land-Tortoises (Testudines). The marine Chelonians generally feed upon vegetables; the Emys and Trionyx approach more nearly to the terrestrial than to the marine species; they are carnivorous, feeding on frogs, fishes, fresh-water mollusca, and other small animals. The Trionyces differ from their congeners in being destitute of a horny external integument, having no scutes on the buckler or any other part of the body but the osseous carapace is invested with a strong tough skin, which equally covers the dorsum and sternum, to which it firmly adheres; the dermal surface of the bones in these Tortoises is always rugose, and either granulated, or covered with punctations and depressions. The buckler of the Trionyces is of a depressed form, with a soft flattened margin. The TestudinidÆ, or land-Tortoises, are too well known to render any description requisite for our present purpose.

In the marine species, eight pairs of ribs and thirteen plates of the longitudinal series form the buckler; the ribs or costal plates are united to each other through a great part of their extent; but towards their distal or outer extremities each rib contracts, and terminates in a point, which is supported on a marginal series of bony plates; the intervals between the ribs are filled up in the living animal by a cartilaginous membrane which never becomes ossified. This character, therefore, affords an important aid in the discrimination of the fossil remains of this family.[679]

In the terrestrial and the marsh Tortoises, the ossification is complete in the adult state; but in the fluviatile Trionyces, which are without a horny integument, there is no border, or marginal series of bony plates, and the extremities of the ribs are therefore always distinct, and generally have an obtuse extremity. The skeletons of the three groups present corresponding modifications, and an accurate knowledge of the osteology of the recent animals is necessary to enable the palÆontologist to arrive at secure conclusions as to the characters and relations of the fossil species.[680] We can only advert to one remarkable osteological character,—the construction of the shoulder, which differs from that of all other animals, in being situated within the cavity of the thorax, instead of without. In consequence of this modification, a process of the shoulder-blade (scapula or omoplate), termed the acromion, is largely developed, and the shoulder-bone is tri-mucronate, or three-pronged, consisting of a short, thick head, containing a concavity (which, with that on the coracoid-bone, forms a socket for the arm-bone), and of two diverging branches. This form is so peculiar, that the collector can be at no loss to recognise the shoulder-bone of a Chelonian, should it come under his notice with other fossil relics (see Foss. Til. For. pl. xix. fig. 11). The shoulder-blade and its associated coracoid-bone undergo certain modifications in the three groups of Turtles, by which the anatomist may pretty certainly determine the terrestrial, fluviatile, or marine character of the animals to which they belonged. The successful application of a perfect knowledge of this department of osteology, is admirably exemplified in the works to which reference has been made; and even but a slight acquaintance with its principles will often enable us to obtain some general information as to the nature and relations of fossil Chelonians.

The student will remember that all the Chelonians are edentulous, i. e. toothless; their bony jaws being covered by horny sheaths, as in birds; these mandibles are therefore the only dental organs that can occur in a fossil state.

Fossil Turtles and Tortoises.[681]—Some of the earliest indications of the presence of Reptiles on our planet are afforded by the foot-prints of Chelonian animals on the surfaces of the layers of sandstone of the Old Red formation at Elgin, and of the New Red in Dumfriesshire, at Storeton, near Liverpool, and at some places in Germany (see Bd. i. p. 259, and p. 265, note). But no osseous remains of the animals of this family have hitherto been found in strata antecedent to the Oolite. The Solenhofen quarries (Kelheim) have yielded the bones and carapaces of several Emydian tortoises, and some remains of Chelonians have been found at Stonesfield, and in the Portland Sandstone.[682] In the Jura limestone at Soleure, two large species of Emydians have been discovered. The Wealden and Purbeck formations abound in Chelonian remains of both fluviatile and marine genera. From the Isle of Purbeck numerous fine examples have been obtained;[683] my own researches in the strata of Tilgate Forest (Foss. Til. For. p. 60) have also brought to light several species, and in particular an interesting Chelonian related to the soft-skinned, fresh-water tortoises, Trionyces (Geol. S. E. p. 255). In the Cretaceous formation of England the remains of these reptiles are not frequent. The Greensand of Cambridgeshire (Rep. Brit. Assoc. 1841, p. 172,) has yielded a marine species, and that of Kent a fine Emydian form (Owen, Monog. 1851); and in the White Chalk a few examples have been obtained, to which we shall hereafter more particularly allude. On the Continent fine examples have been found in the slate of Glaris (see Bd. pl. xxv'.); and in the upper Cretaceous strata of the Netherlands, at Maestricht, and at Melsbroeck, near Brussels, many beautiful specimens of fresh-water tortoises (Emydes), and marine turtles (Chelones), have from time to time been obtained; these are figured and described by Baron Cuvier (Oss. Foss. tom. v. pp. 236, 239). In the Eocene strata of England, several species of Chelonians have been collected; of these eleven belong to the marine genus Chelone; eight to the fresh-water Trionyx; and eight to the marsh-tortoises, Emys and Platemys. The Isle of Sheppey and Hordwell have yielded the majority of these relics; the turtles are smaller than the recent analogues, which now inhabit intertropical latitudes.[684] The Eocene strata of France contain several fresh-water tortoises, some of which are referable to the Emydes, and others to the Trionyces. From the gypsum beds, near Paris, the remains of one or two species of Trionyx have been obtained (Oss. Foss. tom. v. p. 222), of another at Aix, in Provence, and of three or four species in other localities. A fine specimen of fresh-water tortoise from Œningen, near Constance, is described and figured by Professor Bell in Geol. Trans. 2d ser. vol. iii. The fossil remains of TestudinidÆ, or land-tortoises, are exceedingly rare. No well-determined remains are known in the British strata; the impressions of scutes found in the Stonesfield slate, and the foot-prints above described, being the only indications of the existence of these reptiles. The presence of land-tortoises in the strata of France appears to be equally problematical, for the relics obtained from Montmartre and Aix (Oss. Foss. p. 245) afford no certain data as to the character of the original.

The Tertiary formations of India, however, have furnished decided examples of fossil terrestrial tortoises; and among the innumerable relics of the beings of an earlier world, which the indefatigable labours of Dr. Falconer and Captain Cautley have brought to light, and which those accomplished naturalists have so skilfully developed, are the remains of land tortoises of prodigious magnitude (Colossochelys atlas); one specimen indicating a length of twelve or fourteen feet, with a breadth and height of corresponding proportions! These remains are associated with the bones gigantic extinct mammalia, allied to the PalÆotheria and other pachyderms of the eocene deposits of the Paris basin; and with those of Emydian and Crocodilian reptiles.[685]

Fossil Marine Turtles.—In illustration of this subject, I select a specimen discovered in the lower Chalk, at Burham, Kent, which is remarkable for its beautiful state of preservation, and its peculiar osteological characters.

Chelone Benstedi. Lign. 238.—To Mr. Bensted, of Maidstone, whose discoveries have rendered his quarry of Kentish Bag classic ground to the British palÆontologist, I am indebted for this splendid fossil turtle. The quarry whence it was obtained is situated at Burham, a short distance from the banks of the Medway, between Chatham and Maidstone, and presents a good section of the lower Chalk. This locality is rich in fossil remains, rivalling in this respect the quarries near Lewes, Worthing, and Arundel, in Sussex. Two other fossil Turtles have been obtained from this quarry, and now enrich the cabinets of Sir P. Egerton and Mr. Bowerbank. Other relics of Chelonians found in this place are four marginal plates of the carapace, and fragments of ribs,[686] some marginal plates of a much larger individual, mandibles, and other fragments, which are noticed in Prof. Owen’s Monograph, 1851. The specimen, of which Lign. 238 is a reduced figure, consists of the dorsal buckler or carapace almost entire; it is of a depressed elliptical form, with a longitudinal median ridge; it is six inches in length, and three and a half inches in breadth across the middle. It is composed of eight ribs, or costal plates, on each side the dorsal ridge, which is formed of ten neural plates; and there is a border of marginal plates. These plates are united to each other by finely indented sutures, and bear the imprints of the horny scutes, or tortoise-shell, with which they were originally invested. The expanded ribs are united throughout the proximal half of their length, and gradually taper to their marginal extremities, which are supported by the plates of the osseous border.[687] This description applies to the specimen as seen in Lign. 238; but Mr. Bensted so skilfully cleared away the chalk as to admit of the removal of a great part of the dorsal shield, by which means some of the vertebrÆ, four sternal (hyosternal and hyposternal) plates, and one of the coracoid bones are displayed. This brief description will suffice to convey a general idea of the characters of this fossil, which differs from any known recent turtle, and possesses some anomalous features, that appear to indicate some slight Emydian affinities.

Among the numerous fossils obtained from the Chalk of Sussex, the only trace of a Chelonian reptile that has come under my observation is the bony mandible or beak of a Turtle, Lign. 239. Its surface displays a fibrous cancellated structure, denoting the attachment of the horny sheath with which, in a recent state, it was covered. More or less perfect specimens of such mandibles also occur in the Chalk of Kent and elsewhere, but no bones of the skull have yet been met with in that deposit. In the Greensand of Cambridgeshire, however, the cranium of a small turtle has been found. It is figured and described by Prof. Owen as Chelone pulchriceps (Monograph, 1851).

Chelone Bellii. Lign. 240, Petrif. 155.—In the strata of Tilgate Forest, fragments of the carapace, of the plastron or sternum, and of the marginal plates, with some of the bones of the extremities, of a large marine turtle have been discovered; several specimens are figured in Foss. Til. For. pl. vi. and vii. Some examples must have belonged to an individual at least three feet in length. Unfortunately, the specimens hitherto obtained are very imperfect, and do not exhibit essential distinctive characters, with the exception of the ribs, which are united to within a short distance of their distal or marginal extremities; hence the costal interspaces are reduced to much smaller dimensions than in any recent or fossil Turtles with which I have had the means of comparing them. The fragment of a rib, imbedded in Tilgate grit, figured Lign. 240, well exhibits this character.

Fossil fresh-water Tortoises.—The remains of fresh-water Tortoises, referable to the EmydidÆ, occur in the Purbeck and Wealden strata (Owen’s Monograph, 1853, and Rep. Brit. Assoc. 1841); the resemblance of some of these to the Jurassic species from Soleure was noticed by Cuvier (Oss. Foss. vol. v.). Among the Chelonian remains of the Wealden, some of the most remarkable are the costal plates and other bones of a Tortoise, which in its essential characters is closely allied to the Trionyces,[689] but differs from the recent forms, in having possessed a dermal horny integument, formed of scutes of tortoise-shell. The chelonians of the genus Trionyx (so named from their having three claws) have the extremities of the ribs free, and not articulated to a border of marginal plates, and there are intervals between their costal plates even in the adult state. The external surface of the bones of the buckler is covered with granulations, or with little pits, for the attachment of the soft skin, the only integument with which these animals are invested; and, being destitute of horny scutes, their bones exhibit no furrows, as in the other genera. But the fossil rib-plates (see Lign. 241) have a shagreen-like or punctated surface, like the recent Trionyces, and at the same time bear the imprints of horny scutes; and, instead of being nearly of an equal width throughout their entire length, as in the existing species, have one extremity much wider than the other, as in the land-tortoises. From the slight degree of convexity of the ribs, it is evident that the carapace was much flattened, as in the Trionyx.[690] Except in having a defensive dermal integument, and agreeing in this respect with many of the Crocodilian reptiles, with which its bones are associated, the original must have closely resembled the existing predaceous fresh-water soft Turtles; and, doubtless, like those reptiles, inhabited the muddy beds of lakes and rivers, preying upon the eggs and young of the larger reptiles, and on the uniones and other fluviatile mollusca, whose shells are very commonly found imbedded with its remains.

VII. Ophidians, or Serpents. Lign. 242.—The remains of the vertebral columns of extinct Serpents were discovered many years since in the London clay of the Isle of Sheppey, and specimens were obtained by the celebrated Hunter, and preserved in his museum. These specimens, together with others in the collections of Messrs. Saull, Bowerbank, Dixon, Combe, and S. Wood, have been figured and described, and their relations to existing types elaborately worked out, by Professor Owen.[692] The PalÆophis typhÆus, from the Bracklesham clay, had a length of about twenty feet, and, from the compressed character of its caudal vertebrÆ, was probably a sea-serpent. A somewhat smaller species also occurs at Bracklesham. The Sheppey specimens are referred to another species of this extinct genus, namely, the P. toliapicus (Lign. 242); it was from ten to twelve feet in length. The remains of two species of land-serpents, respectively about four and three feet long, have been found at Hordwell Cliff. These belong to the extinct genus Paleryx, thus named in reference to the near affinities of the Hordwell vertebrÆ to those of the recent Eryx, one of the Boa and Python group of serpents.[693]

The vertebrÆ of Serpents are distinguished by a transversely oblong anterior concavity, forming a deep cup, and a corresponding posterior convexity or hall; by the interlocking of the projecting posterior oblique processes with the anterior pair; and by the oblong tubercle on each side of the anterior part of the body of the vertebra, for moveable articulation with the head of the ribs; a spinal column thus constructed combines in the highest degree perfect flexibility with great strength.

In addition to the ophidian relics above referred to, fossil vertebrÆ of a small serpent (PalÆophis?) have been found in the Eocene sand below the Bed Crag, at Kyson in Suffolk;[694] a locality that has yielded other organic remains of great interest (see chap. xix.; and Wond. p. 258). The only fossils of this order of reptiles known to Baron Cuvier appear to have been some vertebrÆ from the bone-breccia of Cette (Oss. Foss. tom. iv. p. 177).

Fossil eggs of snakes are occasionally met with in a comparatively recent limestone, of fresh-water origin, in Germany, near Offenbach, associated with shells of land and fresh-water molluscs. Like the turtles’ eggs on the shores of Ascension Island, these ova were probably laid in the moist mud, and became encrusted and preserved by a deposit of tufa.[695]

VIII. Batrachians.—The reptiles termed Batrachians (from the Greek name for Frog) are characterized by the metamorphoses which they undergo in the progress of their development from the young to the adult state; the Frog, Toad, and Newt are familiar examples of this order. Their organs of aËrial respiration consist of a pair of lungs; but in their young state they are provided with gills, supported, as in fishes, by cartilaginous arches. These organs disappear, in most species, when the animals arrive at maturity; but in a few genera, as the Siren and Proteus, they are persistent. The skeletons of these reptiles present corresponding modifications. The skull is, for the most part, much depressed, and the cerebral cavity small; it is united to the vertebral column by two distinct condyles, situated on the sides of the occipital or cranio-spinal aperture.[696] The vertebral column, in some genera (as, for example, in the common frog), is very short, and is reduced to eight or ten bones, the caudal vertebrÆ being fused into a long cylindrical style; but in the higher organised Batrachians the spine is composed of concavo-convex vertebrÆ, as in the Crocodile: in the lower type, as the Siren, Proteus, and Axolotl, the vertebrÆ are biconcave, as in numerous species of fossil Saurians. The ribs are merely rudimentary, being very short and few; a condition which has relation to the mode of reproduction in these animals, the eggs being accumulated and shed at once.[697] Some of the Batrachians are edentulous, but others have numerous small, conical, uniform, closely-arranged teeth, placed either in a single row, or aggregated like the rasp-teeth in fishes.[698]

Batracholites; or fossil remains of Batrachians.—The skeletons, vestiges of the soft parts, and imprints of the feet of several genera of Batrachians occur in a fossil state in tertiary deposits, all of which, like the existing races, appear to belong to fresh-water or terrestrial species. In the pliocene or newer tertiary strata, on the banks of the Rhine, at Œningen, and in the papierkohle of the Eifel, several species of Frog, Toad, and Newt, have been discovered. Fossil frogs of a small species, very similar to the recent, occur in numbers in a dark shale, overlaid by basalt, in the vicinity of Bombay.[699]

A celebrated fossil of this class is the gigantic Salamander (Cryptobranchus), three feet in length (Lign. 243), found at Œningen (see Wond. pp. 263, 580), which a German physician of some note (Scheuchzer) supposed to be a fossil man![700] and he described it in an essay, entitled "Homo diluvii testis et Theoscopos," as being the moiety, or nearly so, of a human skeleton, with the bones and flesh incorporated in the stone.[701] A fine example of this fossil Salamander is preserved in the British Museum (Petrif. p. 186).

Labyrinthodon. Ly. p. 290-293; Wond. p. 550. By far the most interesting evidence of the existence of Batrachian reptiles in the earlier ages of our planet has been afforded by Professor JÄger’s discovery of the skull, teeth, and other remains of gigantic extinct animals, allied to the Salamander, in the Upper New Red Sandstone (Keuper) of Wirtemberg.[702]

These remains were referred by this eminent physician and naturalist to saurian genera, although the double condyle of the occipital bone indicated Batrachian affinities. It was reserved, however, for our distinguished countryman, Professor Owen, to correct the error into which the German savant had fallen,—remove the obscurity in which the subject was involved,—determine the natural relations of the original,—and develope a modification of dental organization of the most unexpected and interesting character.

Dr. Lloyd, of Leamington, having discovered some fossil teeth and bones in the light-coloured sandstone of the New Red, at Warwick and Leamington, submitted them to Professor Owen, who, struck with their general resemblance to the teeth of the gigantic SalamandroÏdes of Wirtemberg, instituted a microscopic examination of the British and German specimens. The result proved that the teeth from both localities possessed a remarkable and complicated structure, produced by the convergence of numerous inflected folds of the external layer of cement towards the pulp-cavity; to which, as we have already seen (p. 666), a very slight approach was made in the tooth of the Ichthyosaurus, and a still closer approximation by the teeth of certain fishes (Lepidosteus, p. 616). From the intricate meanderings or labyrinthine inflections observable in the sections of these teeth, Professor Owen has given the name of Labyrinthodon to these extinct Batrachian reptiles, and has determined five British species; one of which (L. JÆgeri) he conceives to be identical with a species described by my friend, Dr. JÄger.

The remains of the skeletons of these reptiles, hitherto found in Warwickshire, consist of portions of the cranium, and of the upper and lower jaws, with teeth, vertebrÆ, a sternum, and some of the bones of the pelvis and the extremities. From a specimen (of L. scutulatus) consisting of an aggregated group of bones, imbedded in sandstone, comprising four vertebrÆ, portions of ribs, a humerus, a thigh-bone, and two leg-bones, with several small osseous scutes, it appears that one species, at least, resembled the Crocodiles in its dermal structure. But Professor Owen remarks, that this modification of the dermal system does not affect the claims of the Labyrinthodonts to be considered as Batrachians, although all the known living species of this order are covered with a soft, lubricous, naked integument; for the skin is the seat of the most variable characters in all animals; and the double occipital condyle, the simple lower jaw, the palatal vomerine bones, and the teeth of these fossil reptiles must be deemed decisive of their essentially Batrachian nature.

From the specimens of the cranium the important fact has been ascertained, that the Labyrinthodonts had subterminal nostrils leading to a wide and shallow nasal cavity, which is separated by a broad and almost continuous palatal flooring from the cavity of the mouth; indicating, by its horizontal position, that the posterior apertures were placed far behind the external nostrils; whereas in the recent air-breathing Batrachians the nasal canal is short and vertical, and the inner apertures pierce the anterior part of the palate. The nasal cavities in the Frog are vertical; for this reptile swallows air. The Labyrinthodonts must, therefore, have breathed air like the Crocodiles, and were probably provided with well-developed ribs, and not mere rudimentary styles, as in most living Batrachians.

Tooth of the Labyrinthodon. Pl. VI. fig. 3.—The tooth of the Labyrinthodon is of a conical figure, very slightly recurved, and marked externally with shallow, fine, longitudinal strife. Pl. VI. fig. 3a, represents (¹/₂ nat. size) a specimen presented to me by Dr. JÄger. The tooth is implanted, by a single fang, in an alveolar groove to which it is anchylosed. It consists of a simple central pulp-cavity, surrounded by a body of dentine, which has an external thin coat of cement; and a vertical duplication or fold of this cement penetrates the substance of the tooth at each of the striÆ, which are arranged at intervals of about one line around the entire circumference of the tooth. The inflected folds of cement extend inwards towards the centre, in a straight direction for about half a line, then become undulated, and finally terminate in a dilatation or loop, close to the pulp-cavity, from which it is separated by a thin layer of dentine. Within these inflections of the cement, the dentine, or tooth-bone, is similarly disposed; a layer of dentine lining the folds of cement, and having corresponding interspaces, which are filled up by the processes from the pulp-cavity. It is this blending of the cement and dentine in labyrinthine folds, that gives the peculiar character observable in transverse sections of the teeth. Pl. VI. fig. 3a, represents a transverse section of half the diameter of the tooth; the vacancy in the middle of the line at the bottom is a section of half the pulp-cavity. Fig. 3b is a vertical section of a fragment near the summit of the tooth; and fig. 3c, a highly-magnified view of one of the anfractuosities, showing a fold of cement, surrounding a fold of dentine, and in the centre of the latter the termination of a process of the pulp. The section of the tooth of the Ichthyosaurus, Pl. VI. fig. 9, shows the most simple modification of this structure; the apparent complication of that of the Labyrinthodon arises from the inflections of the three elements of dental organization being more numerous and diversified. But the beautiful plates and the graphic description of the original discoverer must be seen and perused to obtain an adequate idea of the exquisite structure of the fossil teeth; for the distribution of the extremely minute calcigerous tubes of the dentine is as diversified as that of the constituent substances. And even after viewing these chefs-d’oeuvres of structural delineations, should the reader have an opportunity of examining a transverse section of a tooth under the microscope, he will feel how feebly any engraving can represent the characters of the original.[703]

Archegosaurus. Lign. 244, Ly. p. 336, figs. 384,[704] 385.—The occurrence of reptilian remains in deposits of higher antiquity than the Triassic was first established in 1844, by the discovery of the skull and other portions of the skeleton of an air-breathing reptile, the Apateon pedestris, related to the Salamanders, and about three feet in length, in the coal of MÜnster-Appel in Rhenish Bavaria. In 1847 Professor Von Dechen obtained, in nodules of argillaceous ironstone, from the coal-field of Lebach, in the district of SaarbrÜck, three species of the same type of reptiles; these have been described by Goldfuss, under the name of Archegosaurus.[705] One of them was well known to collectors, but had previously been regarded as a fish (the Pygopterus lucius of M. Agassiz).

The skull and portions of the trunk of this species (A. Dechenii), see Lign. 244, indicate an animal three and a half feet in length. Seventeen dorsal vertebrÆ, imprints of the ribs, and remains of the extremities, have been collected. The jaws to beyond the orbit have small fine conical teeth, longitudinally striated. The eye was furnished with an osseous ring. The skin, of which a considerable part was detached, was covered by long, narrow, wedge-shaped, horny scales, arranged in rows (Lign. 244). The cranial bones are characterized by reticulating grooves and pittings, similar in character to the reticulate markings on the cranial bones of the Labyrinthodon, but of a more delicate sculpturing. The original reptiles were quadruped; the fore and hind feet had distinct toes; but the limbs were feeble, and only capable of swimming, or, when on land, of a slow creeping movement.

The Archegosaurus is closely allied to the Labyrinthodonts;[706] and, in the words of Professor Owen,[707] it is "essentially Batrachian, and most nearly allied to the perennibranchiate, or lowest or most fish-like of that Order of Reptiles."

Parabatrachus Colei.—Under this appellation Professor Owen has lately described (Quart. Geol. Journ. vol. ix. p. 67, pl. ii. fig. 1,) a batrachoid fossil, consisting of cranial and maxillary bones with teeth, probably from the shale of the Glasgow coal-field, at Carluke, Lanarkshire. The slab of coal-shale in which the specimen is imbedded contains also a large scale of the Holoptychius (see p. 618).

Dendrerpeton Acadianum.[708] (Quart. Journ. Geol. Soc. 1853, pp. 58-67, plates ii. and iii.)—The remains of a reptile and a land-shell, resembling a Pupa, were discovered in 1852, by Sir C. Lyell and Mr. J. W. Dawson, in the interior of an erect stamp of a fossil tree (Sigillaria), in the coal-measures at the South Joggins cliffs, Nova Scotia. These remains were fully described by Professor Jeffries Wyman, of Harvard University, U. S., and Professor Owen in the Appendix to the Memoir by Sir C. Lyell and Mr. Dawson, in the Journal of the Geological Society, vol. ix. Some of the bones were recognised as having a near resemblance to those of the recent Menobranchus and Menopoma (Perennibranchiate Batrachians, inhabiting North American fresh-waters); the sculptured cranial bones are analogous to those of the Labyrinthodon and Archegosaurus; and the teeth have a Labyrinthodontoid structure: numerous, small, concentrically striated scutes, of an irregular oval shape, accompany the bones and teeth.

The conclusions arrived at by the eminent comparative anatomists to whose examination the remains in question were submitted, show that the character of the fossils are those of Perennibranchiate Batrachians; that, with regard to the long bones, it is not improbable that the corresponding bones in the Archegosaurus (p. 745) and Labyrinthodon (p. 741) would present similar correspondences with those of the existing perennibranchiates; and that, although the Dendrerpeton cannot be referred to any known form of the two genera just mentioned, yet there exists strong evidence of its close affinity with these extinct Batrachians.

The Dendrerpeton Acadianum was probably between two and three feet in length. A series of minute biconcave vertebrÆ were found with the other remains in the erect tree, these, however, from their relatively small size, and from other characteristics, are regarded by Professor Wyman as having probably belonged to some other associated reptile.

The Labyrinthodont reptiles have been regarded as characteristic of the Permian and Triassic epochs, their remains being found in Germany and England in rocks of that age. The commencement of the existence of this family of sauroid-batrachians, however, is of greater antiquity, since their relics also occur in the formations of the Carboniferous epoch. The Archegosaurus (p. 745), a batrachian but slightly removed from the true Labyrinthodont type, has left its well-characterized remains in the Coal of Germany; the Parabatrachus, in that of Scotland; and the allied Dendrerpeton, in the Nova Scotian coal-field. This last-mentioned great carboniferous formation has, however, afforded fossil evidence of the existence of the true Labyrinthodonts in the Coal-period, for some cranial bones, imbedded in a mass of Pictou coal, lately sent to England by Mr. J. W. Dawson, and the subject of a Paper by Professor Owen, read before the Geological Society, were demonstrated by that distinguished palÆontologist to have close affinity with the corresponding parts of the skull of the Triassic genera Capitosaurus and Metopias.

Ichnolites (Foot-prints on stone). Lign. 245.—The sandstones and mud-stones of many localities retain the track-prints of animals that have passed along on the surface of the beds when in a soft state. These foot-prints, or ichnolites, either occur as impressions on the surface originally marked lay the animal in the act of progression, or as the reverse of such impressions, being casts in relief on the under side of the layer covering the surface originally impressed. Such indications of footsteps and trails have been noticed especially in the forest marble, a member of the Lower Oolite series, where Crustacea and Mollusks have left their markings, and in the New Red Sandstone, where the indications of reptilian quadrupeds and of bird-like bipeds[709] have been here and there preserved in great distinctness. Tracks referable to Crustaceans have been found by Mr. W. E. Logan, on the very ancient and rippled surfaces of the Potsdam Sandstone of North America (see p. 543, note); and very lately Mr. J. W. Salter has communicated to the Geological Society the discovery of markings, referred by him to the little entomostracous Hymenocaris (see p. 526), on the Lower Lingula Flags of North Wales,—deposits of as great an age, if not older. The most ancient reptilian ichnolites are those discovered by Capt. L. Brickenden[710] in the Old Red, at Cummingston, near Elgin, which have some resemblance to the track of a club-footed Chelonian (Ly. fig. 521); and those of the Devonian sandstone of Sharp Mountain, Pennsylvania, discovered by Mr. I. Lea,[711] which exhibit distinct toes, and are probably allied to the Cheirotherian ichnolites, about to be mentioned, as are also other ancient fossil foot-tracks in the Carboniferous deposits[712] of Pennsylvania, which are figured and described in Ly. pp. 337-340.

The sandstones of the New Red or Triassic series frequently retain the track-prints of animals, and numerous notices of such occurrences have been published.[713] In addition to the account of these invaluable evidences of the existence of bygone creatures that is here given, the attention of students is especially directed to Dr. Buckland’s most interesting description and illustrations of such as were known when his Treatise was published (Bd. i. p. 259, &c.; and ii. p. 36, pl. xxvi. &c.).

The imprints of the feet of some large quadrupeds, having the fore-paws much smaller than the hinder, have been found in Saxony (see Wond. p. 555, Bd. p. xxvi.); and also in strata of the same age in Warwickshire and Cheshire. The quarries at Storeton Hill, near Liverpool, are celebrated for the abundance and variety of these imprints.[714] Some of the strata of sandstone in this locality are divided by thin beds of clay; a lithological structure which admits of the ready separation of the stone in the direction of the sedimentary planes.

Imprints are found on the face of each successive stratum; and on some of the layers, not only the tracks of animals that have walked over the clay when soft are distinctly observable, but the surface is often traversed with casts of the cracks caused by the desiccation of one layer of clay previously to the deposition of the succeeding layer of sand or mud; and it often presents a blistered or warty appearance, being covered with either little hemispherical eminences or depressions, which an accurate investigation of the phenomenon has proved to have been produced by showers of rain (Ly. figs. 526-528). On the slabs of sandstone, the forms of the sun-cracks, rain-drops, and foot-prints appear in relief, being casts moulded in the soft clayey mud upon which the original impressions were made; while on the clay or shale, corresponding depressions are apparent.[715]

The foot-prints on these strata are of several kinds; some appear to have been produced by small reptiles and crustaceans; but the principal imprints are identical with those which have been observed in Saxony, and are referable to some large quadruped, in which the fore-feet were of a much smaller size than the hind-feet (Lign. 245). From a supposed resemblance of the imprints to those of a human hand, Professor Kaup proposed the name of Cheirotherium, to designate the unknown animal which had left these "footsteps on the sands of Time." But since Professor Owen’s discovery, that the bones and teeth of reptiles found in similar strata in Warwickshire belong to gigantic Batrachians, and since the fore and hind-feet of the frog-tribe are often as dissimilar in size as the impressions of the Cheirotherium, it has been suggested, with much probability, that the foot-prints in question may be those of Labyrinthodonts; but until the form of the feet of these extinct Batrachians can be ascertained, this inference must be regarded as conjectural (Ly. fig. 331).

Allusion has already been made to foot-prints, supposed to be those of tortoises (see p. 729), on slabs of Triassic sandstone in Scotland. Of these there are five species at Corncockle Muir, in Dumfriesshire: they are termed Chelichnus by Sir W. Jardine, who has lately described them in his Ichnology of Annandale, a splendid folio work, illustrated with full-sized lithographs, coloured after nature. They are accompanied with three other forms of footstep (Herpetichnus, Batrachnis, and Actibatis), one of which Sir W. Jardine regards as indicative of an animal probably of a saurian form.

At Grinsill quarry, from which the remains of the Rhynchosaurus (p. 712) were obtained, some small foot-prints have been observed, which, with some probability, have been referred to that animal (Rep. Brit. Assoc. 1841, p. 146).

A beautifully distinct series of foot-prints, with the mark of a trailing tail, on a rippled slab from the New Red of Shrewley Common, Warwickshire, are figured and described by Strickland and Murchison (Geol. Trans. 2d ser. vol. v. pl. xvviii.). This ichnolite has been provisionally assigned by Professor Owen to Labyrinthodon leptognathus.[716] Similar impressions occur in company with other Cheirotherian imprints at Storeton Hill and at Grinshill.

On Collecting the Fossil Remains of Reptiles.—The length to which this article has extended, compels me to omit a retrospect of the geological distribution of fossil reptiles; and I must refer the reader to the brief review of the Age of Reptiles in Wond. p. 568, et seq., and Petrif. p. 147, &c., and close this chapter with some directions for collecting reptilian remains, and a list of a few British localities.[717]

The fossil Teeth of Reptiles are commonly found in as perfect a state of preservation as those of fishes; and require but the usual care for their preservation. But the collector should assiduously search for vestiges of the jaw and cranium; and it is desirable to place in the same drawer any undetermined bones found associated with the teeth; as they may ultimately afford some clue to the nature of the original animal. The microscopical examination of the teeth is to be conducted in the manner previously directed (p. 639); but for valuable specimens the lapidary should be employed, and transverse sections made from near the apex, the middle, and base of the tooth; if due care be taken, several slices may be obtained from one specimen. I have ten slices from one tooth of the Labyrinthodon. The bones imbedded in limestone generally partake of the chemical character of the rock, and are often permeated with calcareous spar; mere fragments, when polished, frequently display the internal structure.

The suggestions for repairing fossil bones (p. 46) render further instructions on that head unnecessary; and the description of the development of the specimen of HylÆosaurus (p. 689) affords a practical lesson to the young collector.

When a vertebra is found in an imperfect state, it should be closely examined on the spot, and, if it present proofs of recent fracture, the detached processes should be sought for; even if the body of a vertebra be imbedded in stone, and the processes appear to have been broken off before it was enveloped in the rock, the corresponding parts will often be found in the same mass of stone. There is in the British Museum a very fine Saurian vertebra imbedded in a large slab of Tilgate stone, in which the spinous process is seen lying in the same block, several inches distant from the centrum or body; when observed in the quarry the latter only was exposed, and I was about to detach it from the slab, for the convenience of carriage, when I perceived indications of the spinous process. The vertebra was therefore allowed to remain, and the stone chiselled away, so as to expose the spine; and the specimen then displayed its present interesting character.

It may frequently happen that a fragment of a large bone,—as, for example, the thigh-bone of the Iguanodon,—may be obtained from a quarry; and after an interval of some weeks the corresponding portions be discovered. This was remarkably exemplified in the first specimen which revealed to me the peculiar characters of the femur of the Iguanodon. The lower part, or condyloid extremity, of a gigantic bone, firmly impacted in a block of Tilgate-grit, was found in a quarry near Cuckfield; it was evidently but a fragment of the fossil, for the fracture was recent; I therefore requested the quarry-men to make diligent search for the corresponding portion, but without success. Several months afterwards, upon a fresh explosion in the quarry, the head of a large bone was found loose among the fallen mass; but there were no indications that it belonged to the specimen previously found; and it was regarded as another relic of some one of the colossal animals whose bones were distributed in the Wealden deposits. Teeth, fragments of bones, and other fossils were from time to time obtained from the same quarry; and among these a huge quadrangular fragment of bone, similar to the enormous mass that had so long been in my possession, and had defied all attempts to ascertain its character.[718] It was some time before it occurred to me, that the three portions of unknown colossal bone might belong to the same specimen; but eventually they were found to correspond, and upon cementing them together, the femur of the Iguanodon was, for the first time, developed.

The figures in Lign. 206 will assist the collector in recognising the different vertebral processes, even when occurring as detached fragments. When specimens are evidently rolled or water-worn, there is, of course, no probability that the corresponding portions will be met with. Every fragment of a bone the nature of which is not obvious should be carefully preserved; for sooner or later its characters may be ascertained. It is scarcely necessary again to remind the collector, that search should be made for indications of the soft parts around the bones; the specimen of the paddle of the Ichthyosaurus (Lign. 215, p. 669), with its integument, must have impressed this fact too strongly on the mind to be soon forgotten. If the impression of the extremities of a bone, of which a fragment only remains, be observed, the block of stone should be preserved, as a cast may be taken, and the entire form of the original be ascertained.

BRITISH LOCALITIES OF FOSSIL REPTILES.

Aust Cliff, near Bristol. Lias. Plesiosaurus.

Barrow-on-Soar. Lias. Ichthyosaurus, Plesiosaurus.

Bath. Lias. Plesiosaurus.

Battle, Sussex. Wealden. Iguanodon, Cetiosaurus, Goniopholis, Chelonians.

Binstead, Isle of Wight. Upper Eocene. Fresh-water Tortoises. Bognor. Lower Eocene. Chelone.

Bolney, Sussex. Wealden. HylÆosaurus, Iguanodon, Chelonia, Goniopholis.

Bracklesham Bay. Middle Eocene. Crocodiles, Serpents, Chelonians. Brighton. Chalk. Vertebra of Mosasaurus or Leiodon.

Bristol. Lias. Ichthyosaurus.

Brook-Point, Isle of Wight. Wealden. Iguanodon, Cetiosaurus, &c.

Burham, near Maidstone. Chalk. Chelone, Dolichosaurus, Pterodactylus.

Bur wash, Sussex. Wealden; quarries in the neighbourhood. Goniopholis, Turtles.

Cambridge. Lower Chalk. Raphiosaurus, Polyptychodon. Charmouth. Lias. Ichthyosaurus.

Charmouth. Lias. Ichthyosaurus.

Cheltenham. Lias. Ichthyosaurus.

Chipping Norton. Oolite. Streptospondylus.

Clayton. Chalk. Coniosaurus.

Corncockle Muir, Dumfries. New Red. Imprints of feet of Reptiles.

Coton-End, Warwickshire. New Red. Labyrinthodon, &c.

Cubbington, Warwickshire. New Red. Labyrinthodon.

Cuckfield. Wealden; quarries in the vicinity. Iguanodon, Pelorosaurus, HylÆosaurus, Trionyx, &c.

Culver Cliff, Isle of Wight. Wealden. Streptospondylus.

Dover. Chalk. Ichthyosaurus, Plesiosaurus.

Garsington, Oxfordshire. Oolite. Cetiosaurus.

Glastonbury. Lias. Ichthyosaurus.

Grinsill, Warwickshire. New Red. Rhynchosaurus.

Guy’s Cliff, Warwick. New Red. Labyrinthodon.

Harwich. London Clay. Chelonia.

Hastings. Wealden. Iguanodon, Pelorosaurus, Goniopholis, Turtles.

Heddington, Oxfordshire. Kimmeridge Clay. Pliosaurus.

Hordwell. Middle Eocene. Crocodiles, Chelonians, Serpents.

Horsham, Sussex. Wealden; quarries in the vicinity. HylÆosaurus, Iguanodon, Goniopholis, Turtles, &c.

Ilminster. Upper Lias. Ichthyosaurus, Teleosaurus.

Kyson, Suffolk. Eocene. Serpent, Lizard.

Leamington. New Red. Labyrinthodon.

Lewes. Chalk. Vertebra; of Mosasaurus or Leiodon.

Lyme Regis. Lias. Pterodactyles, Ichthyosauri, and Plesiosauri in abundance.

Maidstone. Lower Green Sand; quarries near the town; particularly Mr. Bensted’s "Iguanodon quarry." Iguanodon, Plesiosaurus, Polyptychodon, Fresh-water Tortoise.

Malton. Oolite. Megalosaurus.

Market Rasen. Kimmeridge Clay. Pliosaurus.

Norfolk? Chalk. Leiodon: very rare.

Portland, Isle of. Oolite. Turtles.

Purbeck, Isle of. Purbeck. Goniopholis, Chelonians. Kim. Clay. Pliosaurus.

Redland, near Bristol. Magnesian Conglomerate. PalÆosaurus, Thecodontosaurus.

Saltwick. Lias. Teleosaurus.

Sheppey, Isle of. London Clay. Turtles, Serpents, Crocodiles.

Shotover, near Oxford. Kimmeridge Clay. Pliosaurus, Teleosaurus.

Southerham. Chalk. Mosasaurus, Plesiosaurus.

Stonesfield. Oolite. Megalosaurus, Teleosaurus, Pterodactyles.

Stourton, Cheshire. New Red. Foot-prints of reptiles (Cheirotherium), &c.

Street, Somersetshire. Lias. Ichthyosauri and Plesiosauri.

Swanage, Isle of Purbeck. Goniopholis, Chelonians.

Tilgate Forest. Wealden; quarries in various localities. Iguanodon, Megalosaurus, HylÆosaurus, Suchosaurus, Turtles, and Tortoises.

Watchett, Somersetshire. Lias. Plesiosauri, Ichthyosauri.

Warwick, Guy’s Cliff, near. New Red. Labyrinthodon.

Westbrook, Wilts. Kimmeridge Clay. Ichthyosaurus.

Weston, near Bath. Lias. Plesiosaurus.

Whitby, Yorkshire. Lias. Ichthyosauri, Plesiosauri, Teleosaurus.

Wight, Isle of; along the southern shore, near Brook-Point. Wealden. Iguanodon, Cetiosaurus, &c., washed up on the sea-shore.