AND AYES OF NORTH AMERICA. 



241 



The oldest of these have been found by Messrs. Lea, Rogers and Leidy, near to Pottsville, Schuylkill Co., Penna. 

 The first named naturalist referred them to " a four-footed, air-breathing animal, allied to the Saurians," under the 

 name of Sauropus primsevus. At that time the important differences between the Reptilia and Batrachia were not 

 known; had they been, disputes as to the Reptilian or other affinities of these creatures would have been unnecessary. 

 As no remains oertainly referable to Reptiles have been found below the Permian rocks, it is not reasonable to suppose 

 that the tracks are Reptilian, as Agassi/, lias insisted. On the other hand, there can Ik; no doubt that these creatures 

 were air breathers, as Lea has pointed out. To palaeontologists of the present time, there can be no doubt that the 

 Sauropus was a large Batrachian; which position is entirely confirmed by the form of the tracks themselves. 



The tracks which come next in order, are from 2031 feet higher, and were discovered by Wm. M. Gabb, on the 

 valley of the Little Schuylkill River, about : ; mile from the town of Tamaqua, Schuylkill Co., Penna. They are of 

 peculiar form, and much more like those of the Reptiles than either of the; others here mentioned. 



They are on the surface of a, thin irregular shale about sixteen inches in length. There are many impressions on 

 this surface, one of the most abundant of which consists of three or four parallel grooves. Most of the others are in- 

 termediate. The prominent impression is that of the hind foot of an animal of medium size. There are five toes of 

 remarkably slender form, a sole broader than long, and a narrow and rather long tarsus projecting behind. The 

 lengths of the toes are, commencing with the shortest, 1—2—5—3—4, but the extremity of the second extends a little 

 further than that of the fifth. There is no impression certainly referable to claws, though there is a weak impression 

 at the ends of the first and second digits. There has evidently been no palmar membrane. The sole of the metatarsus 

 is transverse, and is separted by a ridge (in the impression; a groove in the foot,) from the tarsal track, showing that 

 the animal may have been usually not plantigrade, but rather as in existing Salamanders. The heel is about as long 

 as the width of the metacarpus, subacuminafe, and most impressed and contracted on the side next the shortest toe. 



Fig. 54. 



Measurements. 



In. 



hill.. 



Total length, 



2 



4 



Length to sole from heel, 





it. 



" of sole to fourth toe, 





5.5 



" " fourth toe, 



1 



23 



Width of sole, 





'.) 



" " heel, 





4 



" between extremities toes, 



1 



5 



The impression of the corresponding foot has been obliterated by subse- 

 quent marks. At; a distance of four inches behind the heel a track of four toes 

 similar to that already described, would appear to pertain to the same animal; 

 they are imperfect, and the heel is broken off with the rock. 



A. single impression remains, whose position, form and size would appear 

 appropriate to the present species. It belongs, like the hind foot, to the right 

 side, the -short toes being on the inner side. Its position is a little (8 lines) be- 

 hind the posterior track, on the inner side, and 2 in. 2.5 lines in advance of the 

 imperfect track mentioned. It consists of the Impressions of four toes, whose; 

 extremities project in the following order: 4 — 1 — 2 — 3. Within the inner (first) 

 toe, there is a short pit, which may be a rudimental 5th toe, and just behind it, 

 an oval depression of the carpus. As in the hind foot, the digits are remarkably 

 slender. 



X 





Length of track, 

 Expanse of foes, 



Lines. 

 0.5 



5.5. 



Some of the frisuloafe impressions are in the line of progress of the animal, 

 and may have been produced by its tail. 



The broad metatarsus of this animal is Batrachian, as is the apparent lack of claws, while the remarkably slender 

 digits constitute a Lacortian feature. The most singular character, the prolonged, narrow tarsus, is not found in any 

 AMEHI. PUILOSO. KOC. — VOL. XIV. — til 



