“Trias” is an arbitrary term applied in geology to the upper division of a vast series of red loams, shales, and sandstones, interposed between the lias and the coal, in the midland and western counties of England. This series is collectively called the “New Red Sandstone formation,” to distinguish it from the “Old Red Sandstone formation,” of similar or identical mineral character, which lies immediately beneath the coal.

The animals which have been restored and placed on the lowest formation of the Secondary Island, are peculiar to the “triassic,” or upper division of the “New Red Sandstone” series, which division consists, in England, of saliferous (salt-including) shales and sandstones, from 1000 to 1500 feet thick in Lancashire and Cheshire, answering to the formation called “Keuper-sandstone” by the German geologists; and of sandstone and quartzose conglomerate of 600 feet in thickness, answering to the German “Bunter-sandstone.”

The largest and most characteristic animals of the trias are reptiles of the order

Batrachia.

The name of this order is from the Greek word batrachos, signifying a frog: and the order is represented in the present animal-population of England by a few diminutive species of frogs, toads, and newts, or water-salamanders. But, at the period of the deposition of the new red sandstone, in the present counties of Warwick and Cheshire, the shores of the ancient sea, which were then formed by that sandy deposit, were trodden by reptiles, having the essential bony characters of the Batrachia, but combining these with other bony characters of crocodiles and lizards; and exhibiting both under a bulk which is made manifest by the restoration of the largest known species, (No. 16), occupying the extreme promontory of the Island, illustrative of the lowest and oldest deposits of the secondary series of rocks. The species in question is called the—

No. 18.—Labyrinthodon Salamandroides.

or the Salamander-like Labyrinthodon; the latter term being from the Greek, signifying the peculiar structure of the teeth, which differ from all other reptiles in the huge Batrachia in question, by reason of the complex labyrinthic interblending of the different substances composing the teeth. The skull of the Labyrinthodon is attached to the neck-bones by two joints or condyles, and the teeth are situated both on the proper jaw-bones, and on the bone of the roof of the mouth called “vomer:” both these characters are only found at the present day in the frogs and salamanders. The hind-foot of the Labyrinthodon was also, as in the toad and frog, much larger than the fore-foot; and the innermost digit in both was short and turned in, like a thumb.

Consecutive impressions of the prints of these feet have been traced for many steps in succession (as is accurately represented in the new red sandstone part of the Secondary Island) in quarries of that formation in Warwickshire, Cheshire, and also in Lancashire, more especially at a quarry of a whitish quartzose sandstone at Storton Hill, a few miles from Liverpool. The foot-marks 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 foot-prints as in moulds. The impressions of the hind-foot are generally eight inches in length and five 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, four inches long and three inches wide, occurs. The footsteps follow each other in pairs, each pair in the same line, at intervals of about fourteen inches from pair to pair. The large as well as the small steps show the thumb-like toe alternately on the right and left side, each step making a print of five toes.

Foot-prints 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 impression project in high relief, and afford models of the feet, toes, and claws of the animals which trod on the clay.

Similar foot-prints were first observed in Saxony, at the village of Hessberg, near Hillburghausen, in several quarries of a gray 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, proposed the name of Cheirotherium (Gr. 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. The discovery, however, of fossil skulls, jaws, teeth, and a few other bones in the sandstones exhibiting the footprints in question, has rendered it more probable that both the footprints and the fossils are evidences of the same kind of huge extinct Batrachian reptiles.