part ii^{me.} chap. ii.: and Prof. Owen’s _Monographs_, published by

the Palæontographical Society, 1849, 1851, 1853. The Penny Cyclopædia, _Art._ Tortoises, contains an excellent summary of the osteology of these reptiles, also an abstract of Professor Owen’s Report on the Fossil _Chelonia_.

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.

[Sidenote: TURTLES AND TORTOISES.]

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.

[681] See _Rep. Brit. Assoc._ 1841, pp. 168, et seq.

[682] See _Rep. Brit. Assoc._ 1841. pp. 160 and 169.

[683] Some of the most beautiful of these almost perfect specimens have lately been figured and described by Prof. Owen in his Monograph on the Fossil Chelonian Reptiles of the Wealden and the Purbeck; Palæontographical Society, 1853.

[684] Rep. Brit. Assoc. 1841, p. 177, and Monograph on Fossil Reptiles, Pal. Soc. 1849, in which the anatomical details are given with the characteristic accuracy and minuteness of the author.

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]

[685] _Petrif._ pp. 11 and 468.

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.

[686] See _Geol. Proceed_, vol. iii. p. 299.

[687] See also _Phil. Trans._ 1841, p. 153, pl. xi. and xii.; and _Palæontograph. Monograph_, 1851, p. 4, plates i. ii. and iii.

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.

_a._ The striated pointed extremity of rib.

_b._ The distal portion of the costal plate.

[688] The remains of this reptile were noticed in the "Fossils of the South Downs, or Illustrations of Geology of Sussex," 4to. 1822, p. 47, and subsequently figured in the "Illustrations of the Geology of Sussex, with figures and descriptions of the Fossils of Tilgate Forest," 4to. 1827, p. 60, pl. vi. and vii.; and this extinct _Chelone_ was regarded as a species, characterized by the great development of the rib-plates, and named after Professor Bell, the eminent zoologist, in the first Edition of the "Medals." But in the _Monograph_, _Weald. Rept._ 1853, this determination has lately been overlooked; and the specimen figured _Tilg. Foss._ pl. vi. _fig._ 2, is referred to the newly named _Ch. costata_, characterized by its broad and prominent ribs. A third name even (_Ch. Mantelli_) has been bestowed on this interesting fossil, by a German palæontologist.

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.

[689] The relations of these peculiar remains to _Trionyx_ were pointed out in _Foss. S. D._ 1822, p. 47.

[690] See _Petrif._ p. 157, &c.

[691] This Tortoise, with the sanction of Baron Cuvier, was described under the name _Trionyx_, in _Foss. Tilg. For._ 1827, p. 60, and its distinctive characters were pointed out. In _Geol. S. E._ 1833, p. 255, the specific name _Bakewelli_ was proposed in honour of the late Robert Bakewell, Esq., whose excellent works have so greatly promoted the advancement of geology; a privilege to which, as the original discoverer of the species, and of its zoological relations, I was fairly entitled. But this name does not appear in the list of British Chelonians, either in _Rep. Brit. Assoc._ 1841, or in Mr. Morris’s _Cat. Brit. Org. Rem._ 1843. With a melancholy pleasure I now restore the name of my lamented friend, as a just, but very inadequate tribute of respect to his memory.

[Sidenote: FOSSIL SERPENTS.]

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]

[692] Geol. Trans. 2d ser. vol. vi. p. 209, &c. pl. xxii.; Rep. Brit. Assoc. 1841, p. 180; "Dixon’s Geology and Fossils of Sussex," pp. 211-217, pl. xii. _fig._ 14; and especially Palæontographical Monograph, 1850, p. 51, _et seq._; and plates xii. to xvi.

[693] See Monograph on Eocene Reptiles, 1850, from which these notices of the Eocene Ophidians are abridged.

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).

[694] Rep. Brit. Assoc. 1841, p. 181; and Monograph, 1850, p. 66.

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]

[695] Quart. Journ. Geol. Soc. vol. vi. part 2, p. 42.

[Sidenote: BATRACHIANS.]

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]

[696] Saurians, like birds, have a single occipital condyle.

[697] See Dr. Roget’s _Bridgewater Essay_, p. 395.

[698] The variations in the dental system of these animals are given in _Odontography_, chap. ii. p. 187.

[Sidenote: FOSSIL BATRACHIANS.]

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]

[699] Quart. Geol. Journ. vol. iii. p. 221.

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).

[700] Phil. Trans, for 1726, vol. xxxiv.

[701] Ample description and figures of this highly interesting fossil are given by Cuvier, _Oss. Foss._ tom. v. part ii. p. 431, pl. xxv. xxvi.

[Sidenote: LABYRINTHODON.]

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]

[702] Über die Fossile Reptilien welche in Würtemberg aufgefunden worden sind, von Dr. Geo. Friedr. Jäger. 4to. Stuttgart, 1828. See also Hermann von Meyer’s Notice of the Saurians of the Muschelkalk, Banter Sandstein, and Keuper, _Quart. Geol. Journ._ vol. iv. pt. ii. p. 40.

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. 3^a_, 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. 3^a_, 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. 3^b_ is a vertical section of a fragment near the summit of the tooth; and _fig. 3^c_, 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’œuvres_ 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]

[703] Professor Owen’s Memoir on the Labyrinthodonts, in _Geol. Trans._ 2d ser. vol. vi. pp. 503-543, with five admirable lithographs by that excellent artist, Mr. Scharf, and the description of the structure of the teeth, _Odontography_, p. 195, pl. lxiii. lxiv. should be consulted. See also _Cyclop. Anat._ Art. Teeth.

[Sidenote: ARCHEGOSAURUS.]

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).

[704] The original of this figure of _Archegosaurus minor_ is now in the British Museum.

[705] See a notice of the researches of Goldfuss, Von Dechen, and Von Meyer in the geological and zoological history of this interesting group of batrachoid reptiles, _Quart. Journ. Geol. Soc._ vol. iv. part ii. (Miscell.) p. 513, _et seq._

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."

[706] We may remark that in the opinion of Dr. Goldfuss and Von Meyer (_loc. cit._) the Labyrinthodon and the Archegosaurus are saurian forms connecting the Crocodiles and the Lizards, and representing in the ancient fauna an arrested or "permanent larva-condition of the loricated reptiles, as the sirens do among the recent batrachians." Professor Owen’s estimation of the affinities of these genera is stated above, and in the _note_ at p. 55, Geol. Journ. vol. iv. part ii.

[707] Quart. Geol. Journ. vol. ix. p. 69.

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).

[Sidenote: DENDRERPETON ACADIANUM.]

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.

[708] The _Tree-reptile of Acadia_ (Acadia being the ancient Indian name for Nova Scotia).

Fig. 1.--The cranium and part of the lower jaw.

2.--A portion of the skin, or dermal scutes, magnified.

3 and 4.--Magnified figures of two 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_.

[Sidenote: ICHNOLITES.]

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.

[709] See Ornithoidichnites, in chap, xviii.

[710] Quart. Geol. Journ. vol. viii. p. 97, pl. iii.

[711] Across the ridges of the ripples on this slab is a narrow groove, passing along between the two rows of foot-prints; this might have been made by the body or the tail of the animal. _Rep. Brit. Assoc._ 1849, Sect. pp. 56 and 134; and _Trans. Americ. Phil. Soc._ new series, vol. x. part ii. plates xxxi. and xxxii.

[712] With regard to the distribution of reptilian life during the carboniferous and succeeding epochs, see above, page 748.

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.).

[713] The following are the principal notices of ichnolites by English authors which are not referred to in the text:--Cunningham, Yates, and Egerton on Cheirotherian traces in Cheshire, _Geol. Proc._ vol. iii. pp. 12-15; Dr. Black on foot-prints at Runcorn, _Quart. Geol. Journ._ vol. ii. p. 65, pl. ii.; Mr. Cunningham. _Liverpool Lit. and Phil. Proc._ 1848, p. 129, plates iii.-v.; Mr. Hawkshaw on the New Red with foot-prints at Lymm, _Rep. Brit. Assoc._ 1842, Sect. p. 56; Mr. Rawlinson on the same, _Quart. Geol. Journ._ vol. ix. p. 37; Prof. Harkness on the track-bearing beds of Dumfriesshire, _Rep. Brit. Assoc._ 1850, Sect. p. 83; _Quart. Geol. Journ._ vol. vi. pp. 389 and 393; and _Annals Nat. Hist._ 1850, vol. vi. p. 203; Sir W. Jardine, _Annals Nat. Hist._ _loc. cit._ Foreign authorities may be found by reference to Pictet’s _Traité de Paléontologie_, a new and enlarged edition, vol. i. 1853, p. 567, _et seq._

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.

[714] The Museums at Warwick, Warrington, and Liverpool are rich in impressed slabs from the Triassic districts. Numerous fine specimens may be also seen in the Museum of the Geological Society, Somerset House, the Museum of Practical Geology, in Jermyn Street, and in the British Museum (see _Petrif._ pp. 14 and 63).

[Sidenote: RAIN-PRINTS ON STONE.]

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]

[715] The impressions of rain-drops on stone were first noticed, and their origin explained, by Mr. Cunningham. _Geol. Proc._ vol. iii. p. 99. See also an interesting Paper by Sir C. Lyell, _Quart. Geol. Journ._ vol. vii. p. 240.

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).

[Sidenote: CHEIROTHERIUM.]

Fig. 1.--Casts of the imprints of a hind and a fore-foot of the same animal.

2.--Similar tracks of another individual on the same stone.

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.

[716] Geol. Trans. 2d ser. vol. vi. p. 525. The probable relations of _Cheirotherium Hercules_ to _Labyrinthodon Jægeri_, and of _Ch. Kaupii_ to _L. pachygnathus_, are pointed out by the same high authority, _ibid._ pp. 537, 538.

[Sidenote: ON COLLECTING FOSSIL REPTILES.]

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]

[717] An able Summary on British Fossil Reptiles is appended to Prof. Owen’s Report, _Rep. Brit. Assoc._ 1841, p. 191.

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.

[718] The fragment alluded to is figured, _Foss. Til. For._ pl. xviii.

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.