AMPHIBICHNITES.
Genus Camtartimuum.—Fig. 68 gives a reduced view of a portion of new red sandstone, with three pairs of footprints in relief : the first and third of the left, the second of the right, side. Consecutive impressions of such prints have been traced for many steps in succession in quarries of that forma tion in Warwickshire and Cheshire, more especially at a quarry of a whitish quartzose sandstcie at Storton Hill, a few miles from Liverpool. The footmarks are partly concave and partly in relief ; the former are seen upon the upper surface of the sandstone slabs, but those in relief are only upon the lower surfaces, being in fact natural casts, formed on the subjacent footprints as in moulds. The impressions of the hind foot are generally 8 inches in length and 5 inches in width ; near each large footstep, and at a regular distance— about an inch and a half—before it, a smaller print of the fore foot, 4 inches long and 3 inches wide, occurs. The footsteps follow each other in pairs, each pair in the same line, at intervals of about 14 inches from pair to pair. The large as well as the small steps show the thumb-like outermost toe alternately on the right and left side, each step making a print of five toes.
Footprints of corresponding form, but of smaller size, have been discovered in the quarry at Storton Hill, imprinted on five thin beds of clay, lying one upon another in the same quarry, and separated by beds of sandstone. From the lower surface of the sandstone layers the solid casts of each impres sion project in high relief, and afford models of the feet, toes, and claws of the animals which trod on the clay.
Similar footprints were first observed in Saxony, at the village of Hessburgh, near Hillburghausen, in several quarries of a grey quartzose sandstone, alternating with beds of red sandstone, and of the same geological age as the sandstones of England that had been trodden by the same strange animal. The German geologist who first described them (1834) pro posed the name of Cheirotherium (cheir, the hand, therion, beast) for the great unknown animal that had left the foot prints, in consequence of the resemblance, both of the fore and hind feet, to the impression of a human hand ; and Dr. Kaup
conjectured that the animal might be a large species of the opossum kind ; but in Didelphys the thumb is on the inner side of the hind-foot. The fossil skulls, jaws, teeth, and a few other bones, in the sandstones exhibiting the footprints in question, and corresponding in size with those impressions, belong to labyrinthodont or huge extinct batrachian reptiles.
The impressions of the Cheirotherium resemble those of the footprints of a salamander, in having the short outer toe of the hind foot projecting at a right angle to the line of the mid toe, but are not identical with those of any known Batrachia' n or other reptile. They show a papillose integu ment as in some mammals, but also like that on the sole of certain Geckos, and which may be another mark of sauroid departure from the modem batrachian type. The proximity of the right and left prints to the median line indicates a narrower form of body, or its greater elevation upon longer and more vertical limbs, than in tailless Batrachia. In the attempt to solve the difficult problem of the nature of the animal which has impressed the new red sandstone with the cheirotherian footprints, we cannot overlook the fact, that we have in the Labyrinthodons also batrachoid reptiles, differing as remarkably from all known Batrachia, and from all other reptiles, in the structure of their teeth ; both the footsteps and the fossils are, moreover, peculiar to the new red sandstone ; the different size of the footprints referred to different species of Cheiro theria correspond with the different size of ascertained species of Labyrinthodon ; and the present facts best support the hypothesis, that the footprints called "cheirotherian," are those of labyrinthodont reptiles.