Foot-prints of Labyrinthodon (Cheirotherium).

as at Binks, Eskdale, which have received the name of Protichnites Scoticus.*

AMPHIBICHNITES.

Genus CHEIROTHERIUM. -Fig. 83 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 the trias of Warwickshire and Cheshire, more especially at a quarry of a whitish quartzose sandstone at Storton Hill, a few miles from Liverpool. The footmarks are shewn by the impressions, and also in relief; the former are seen upon the upper surface, those in relief upon the lower surface of the sandstone slabs, when raised from their natural position; the latter being casts, formed on the subjacent footprints as in moulds. The impres

* Harkness and Salter "On the Lowest Rocks of Eskdale," Quarterly Journal of the Geological Society, vol. xii., pp. 238, 243, fig. 2.

sions 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 shew 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 thin beds of clay, separated by layers 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 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) proposed the name of Cheirotherium (cheir, the hand, therion, beast) for the unknown animal that had left the footprints, 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 which have been found in the sandstones exhibiting these footprints, and which alone correspond in size with them, belong to labyrinthodont 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 nearly at a right angle to the line

of the mid toe, but are not identical with those of any known Batrachian or other reptile. They shew a papillose integument 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 modern 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 limbs longer and more vertical than in tailless Batrachia, and in strength and proportions more like those of mammals. 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 Cheirotheria 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.

Genus OTOZOUM.-The footprints in the red sandstones, probably of liassic age, in Connecticut, described by Prof. Hitchcock under the above name, equalled in size the largest of those of the Cheirotherium (Ch. Hercules), but the hind foot had but four toes, whilst the fore foot had five toes. It would seem that the hind foot, which was larger than the fore foot, obliterated the print of that foot, by being placed upon it in walking. In the few instances of the fore foot print the toes are turned outward, and the fourth and fifth seem to have been connate at their base. An impression of a web has been clearly discerned in the hind foot. Only one toe on this foot shews a claw, the rest are terminated by "pellets," as in the Batrachia, to which family Dr. Hitchcock refers

these footprints, though with a surmise of the possibility of their marsupial nature.*

Genus BATRACHOPUS (Batrachopus primarus, King.)-In 1844, Dr. King of Greensburg, Pennsylvania, discovered fossil footmarks, which he announced as being those of a reptile, in the sandstone of the coal measures, near that town. No reptilian footprints had previously been found lower in the series than the New Red sandstone. Dr. King states the impressions to be "near 800 feet beneath the topmost stratum of the coal formation."

Sir C. Lyell, in Silliman's Journal, July 1846, describes his visit to Greensburg, where he examined these footmarks, and confirmed Dr. King's description of them. He considered them to be allied to the labyrinthodont footprints which have been referred to the genus Cheirotherium. He says "They consist, as before stated, of the tracks of a large reptilian quadruped, in a sandstone in the middle of the carboniferous series, a fact full of novelty and interest; for here in Pennsylvania, for the first time, we meet with evidence of the existence of air-breathing quadrupeds capable of roaming in those forests where the Sigillaria, Lepidodendron, Caulopteris, Calamites, ferns, and other plants flourished."

These footmarks were first observed standing out in relief from the lower surface of slabs of sandstone resting on thin layers of fine unctuous clay, which also exhibited the cracks due to shrinking and drying. Now these cracks, where they traversed the foot-prints, had produced distortion in them, for the mud must have been soft when the animal walked over it. and left the impressions; whereas, when it afterwards dried up and shrunk, it would be too hard to receive such indentations, and could only affect them in the way of subsequent dislocation. No less than twenty-three footsteps, the greater part so - arranged as to imply that they were made successively by the * Ichnology of Massachusetts, 4to, 1858, p. 123.

same animal, were observed in the same quarry. Everywhere there was a double row of tracks, and in each row they occur in pairs, each pair consisting of a hind and fore foot, and each being at nearly equal distances from the next pair. The hind foot-print is about one-third larger than the fore foot-print: it has five toes, but the front one only four; some of them exhibit a stunted rudiment of the innermost toe or "pollex," which is the undeveloped one. The outermost toe in the hind foot-print is shorter and rather thicker than the rest, and stands out, as it does in fig. 83, like a thumb on the wrong side of the hand.

With this general resemblance to the footprints of Labyrinthodon, from the new red sandstones of Europe, there are well-marked distinctions. In the first place, the right and left series of impressions are wider apart, indicative of a broaderbodied animal. The front print in Batrachopus has only four well-developed toes instead of five, as in Labyrinthodon; it is also proportionably larger, the fore foot in Labyrinthodon being less than half the size of the hind foot. The distance between the fore and hind print of each pair, and of one such pair from the next on the same side, is nearly the same in Batrachopus and Labyrinthodon.

Genus SAUROPUS, Rogers.-Very similar foot-prints were discovered and described by Mr. Isaac Lea in a formation of red shales, at the base of the coal measures at Pottsville, 78 miles N.E. of Philadelphia. These are of older date than the preceding, inasmuch as a thickness of 1700 feet of strata intervenes between the foot-prints at Greensfield and the Pottsville impressions.

Professor H. D. Rogers, in 1851, announced his discovery in the same red shales, between the Devonian and Carboniferous series, of three species of four-footed animals, which he deems to have been rather saurian than batrachian, seeing that each foot was five-toed; one species, the largest of the