196 BRITISH FOSSIL REPTILES. 



fested in other parts of their organisation by the larger Labyrinthodons. As 

 these detached superficial bones are the most liable to be separated from the 

 fragmentary skeleton of the individual they once clothed, the mere negative 

 fact of their absence, when so small a porportion of the bones of the trunk of any 

 Labyrinthodon has yet been found, is insufficient to prove a difference of dermal 

 structure between the Leamington and Warwickshire species. 



No anatomist, indeed, can contemplate the extensive development and bold 

 sculpturing of the dermal surface of the cranial bones in the Labyrinthodontes 

 pachygnathus and leptogiiatlms, without a suspicion that the same character may 

 have been manifested in bony plates of the skin in other parts of the body. And 

 granting that this structure existed, to what extent, it may be asked, does it affect 

 the claims of the Labyrinthodon to be admitted into the order of Batrachia, in 

 which every known species is covered with a soft, lubricous, and naked integu- 

 ment ? To this question it may be replied, that the skin is the seat of the most 

 variable characters in all animals ; and, if considered apart from the modifica- 

 tions of the osseous and dental systems, is apt to mislead the naturalist who is in 

 quest of the real affinities of a species. Suppose, for example, that the existing 

 Chelonian Reptiles were exclusively mud-tortoises, or with a soft and naked skin, 

 as in the species of Trionyx and SijJiargis, would the discovery of the osseous 

 carapace of a true Testudo, in a fossil state, in connection with a skeleton in other 

 respects essentially corresponding with the modifications exhibited by a Trionyx 

 prohibit the association of the fossil in the same order of Reptiles with the Trionyx, 

 because of the indication of the scutes ? It unquestionably ought not to affect 

 such a determination. And so with respect to the Labyrinthodont Batrachia ; if 

 all the species have pushed their affinities to the Crocodilians so far as to have had 

 their trunk defended by bony dermal plates, yet their double occipital condyle, 

 their comparatively simple lower jaw, their large vomerine boiies and teeth are 

 decisive of their Batrachian nature. 



In the " Alaunschiefer of the German Keuper " was found the occipital part of 

 a fossil skull, with a dovible condyle to which the name Salamandroides giganteus 

 was given by Jaeger. I am of opinion that, with the Mastodonsaurus, it was also 

 a Labyrinthodont. 



These extinct forms deviated from existing Salamanders in the crocodilian 

 development and sculpturing of the cranial bones, and iu having dermal osseous 

 plates. Finally, I have to offer remarks, on the Batrachian affinity indicated by 

 their foot-prints. 



Since the above-described fossils were submitted to my examination impres- 

 sions and reliefs of impressions of foot-prints have been found on slabs of the 

 New Red Sandstone in different British localities, proclaiming the primitive 



