o 



01 



stone of Pennsylvania, in 1847, by Dr. Shelley, and described 

 by Isaac Lea, Esq., in a valuable paper published in the Journal 

 of the Academy of Natural Sciences, 1852, under the name of 

 Clepsysaurus Pennsijlv aniens. 



Not only footprints, but bones of these animals have been 

 found in the Triassic strata, in England and in Germany. The 

 head and teeth, vertebrce, pelvis, and bones of the extremities 

 have been examined by Prof. Owen, who has constructed an 

 animal intermediate between the crocodile and the frog. From 

 the labyrinthic structure of the teeth, resembling somewhat that 

 of the teeth of Ichthyosaurus, he called the animal Lahyrintho- 

 don ; Cheirotherium and Labyrinthodon, therefore, are terms 

 applied by him to the same animal. 



The cast exhibited to the Society, is of a specimen from the 

 Keuper coal-beds at Gailsdorf, in Wurtemberg; the original is in 

 the Museum at Stuttgart. This head is figured, and briefly de- 

 scribed by Pictet, in Vol. I. of his " Traite de PaliEontologie," the 

 latest authority (1853) in my possession. Pictet calls it Mas- 

 todonsaurus instead of Labyrinthodon ; the synonyms are 

 Labyrinthodon Jaegeri Owen, Mastodonsaiirus Jaegeri Alberti, 

 Salamandroides giganteus Jaeger, Mastodonsaurus giganteus 

 Quenstedt. Besides the 31. giganteus, Pictet alludes to 31. Vas- 

 lenensis de Meyer, undescribed, and 31. 3Ieyeri Miinster, and 

 31. Andriani Miinster both of which are doubtful species. Pic- 

 tet is of opinion that the five species of Labyrinthodon, described 

 by Owen, may not belong to the species called above Mastodon- 

 saurus Jaegeri. 



The length of the head, which comprises only the cranium 

 and the upper jaw, is two feet four inches, and its greatest width, 

 posteriorly, two feet. The general shape of the head is like that 

 of the frog ; but the broad, much depressed, and flattened max- 

 illary and facial surfaces of the skull, and the coarse sculpturings 

 of the outer surface, resemble those of the crocodile. It resem- 

 bles the frog in the double occipital condyles — in the narrowness 

 of the palatal processes of the superior maxillary, which do not 

 reach to the middle line, — and in the formation of the osseous 

 roof of the mouth, principally by a pair of broad flat bones, 

 analogous to a divided vomer of great extent. 



