A LOWER JAW OF LABYRIXMODON. 2S3 



EXPLANATION OF PLATE XIX. 



Fig. 1. E eternal view of posterior pirt of right ramus of lower jaw. 

 f. Internal aspect of the same specimen. 



3. Articular region, seen from aboye. 



4. Chevron bone. 



a, splenial bone ; b, dentary bone ; c, angular bona ; d, sur angular bone 

 e, articular bone. 



Discussion. 



Mr. Ussher remarked that the Trias of South D^von was too 

 variable in character to furnish reliable evidence as to the persistence 

 of individual beds as lithological or pakeontological zones. The con- 

 glomerate bed of Otterton Point, which crops out below High-Peake 

 Hill, is cut out at Ladram Bay by a fault, but reappears towards 

 Otterton Point for a distance of a mile and a half. It varies very 

 much in character, and exhibits false bedding in parts. Organic 

 remains have been found in the Trias at Kuishton, in a marly gritty 

 conglomerate, which contains Labyriuthodon, Esthcria, &c. — also near 

 Stoke St. Mary's, where Estheria minuta occurs, — in the Vale of 

 Taunton, in sandstone not contemporaneous with that on the coast, 

 and at North Curry, where Esther ice and plant-remains are found in 

 arenaceous beds under marl. 



Mr. WniTAKER stated that while Mr. Lavis's Labyr'mthodon was 

 obtained from near the top of the sandstone, his Ifyperodcijiedoii 

 came from near its base. 



Prof. Ramsay remarked that all these bones were from the 

 Keuper, and not from the Bunter. 



The President (Prof. Duncan) said that Professor Seeley had very 

 properly treated this bone from his own point of view ; but he would no 

 doubt admit that there were others from which it might be looked at. 

 It seemed to him that if this were the lower jaw of LabyrintJiodon, it 

 was very distinct from any other specimen. He noticed that from Mr. 

 Miall's description it would seem that he had got upon the trace of the 

 surangular bone in Diadetogwtthm, as in one of his specimens he 

 describes a ridge which may be the indication of a bone wanting in 

 the Warwickshire specimen but present in this one. He thought 

 that some fish exhibited a somewhat similar construction, but that 

 the lower jaw alone could never be sufficient for the purpose of 

 classification ; and here the other and more essential parts of the 

 skull were wanting. The Labyrinthodonts seemed to him to he 

 unquestionably an order of Amphibia. 



Mr. Lavis, in reply, said that his estimate of the upthrow was 

 made from the lithological characters of the beds. The zone indi- 

 cated by him was not conspicuous by its lithological characters. It 

 contained small grains of quartzite and pockets of marl. 



Prof. Seeley, after thanking the President for his remarks, stated 

 Q. J. G. S. No. 127. x 



