Genus OTOZOUL—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), ereule,$), 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 shows a claw, the rest are terminated by "pellets," as in the Batraehia, to which family Dr. Hitchcock refers these footprints, though with a surmise of the possibility of their marsupial nature..
Genus BATRACHOPUS (Batrachopus prinuevus, 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 Sillirnan'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 Cheirotheriunt. He says—" They consist, as before stated, of the tracks of a large reptilian quad ruped, 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 footprints, 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 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 footprint is shorter and rather thicker than the rest, and stands out like a thumb on the wrong side of the hand.
With this general resemblance to the footprints of Laby rinthodon, 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 broader-bodied animaL The front print in Batrach,opus has only four well-developed toes instead of five, as in Lapin thod,on ; it is also proportionably larger,—the fore foot in Labyritahodon 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 Ba,trachopus and Labyrintkodon.
Genus SAUROPUS, Rogers.—Very similar footprints 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 footprints at Greenfield and the Potts ville 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 three, pre sented a diameter for each footprint of about two inches, and showed the fore and hind feet to be nearly equal in dimensions. It exhibits a length of stride of about nine inches, and a breadth between the right and left footsteps of nearly four inches. The impressions of the hind feet are but little in the rear of the fore feet. With these footmarks were associated shrinkage cracks, such as are caused by the sun's heat upon mud, and rain-drop pittings, with the signs of the trickling of water on a wet beach,—all confirming the conclusions derived from the footprints, that the quadrupeds belonged to air-breathers, and not to a class of animals living in and breathing water.