278 H. G. SEELET ON A PORTION OE 



32. On the Posterior Portion of a Lower Jaw of Ldbyrinihodon 

 (L. Lavisi), from the Trias of Sidmotjth. By Harry Govier 

 Seelev, Esq., E.L.S.,E.Z.S., E.G.S., Professor of Physical Geo- 

 graphy in Bedford College, London. (Read March 22, 1876.) 



[Plate XIX.] 



Notwithstanding all that has been done of late years by Prof. Hux- 

 ley and those who have continued his labours, for the elucidation of 

 the Labyrinthodontia, less is probably known of the structure and 

 affinities of that group than of any other long-established Order of 

 vertebrates. It may perhaps be an open question whether Laby- 

 rinthodonts can rightly be referred to an existing class of animals; 

 for the nature of the affinities of these fossils with Amphibia, Pakeo- 

 sauria, and lleptilia is a subject rather for inquiry than for dogma- 

 tism ; and unfortunately the new materials now to be described are 

 too few- to do more than slightly modify accepted surmises. 



No apology seems to be necessary for the restoration of Prof. 

 Owen's name Labyrinthodon, because neither Prof. Huxley nor Mr. 

 Mi all have attempted to justify either its suppression or reconstruc- 

 tion, while I am inclined to urge that demonstration is wanting tbat 

 any foreign Labyrinthoclont genus, such as Mastodonsaurus, has ever 

 occurred in the British Isles. The single dermal plate figured by 

 Mr. Mi all, so similar to one hereinafter described from Siclmouth, 

 seems to me no evidence ; for Labyrinthodonts like Crocodilia and 

 Teleosauria may well have resembled each other in the dermal ar- 

 mour of allied genera; and in describing an English fossil closely 

 allied to one of those originally described by Prof. Owen from War- 

 wickshire, it seems better to refer it to the genus Labyrinthodon as 

 constituted by Prof. Owen, there being no evidence adduced or avail- 

 able for the subdivision of that genus in the manner proposed by 

 Mr. Mi all. 



To H. J. J. Lavis, Esq., F.G.S., we are indebted not only for the 

 discovery of the present specimen, unexampled among Labyrin- 

 thoclont remains for its beautiful preservation, but also for untiring- 

 labour and skill in extricating the fossil from the matrix, and re- 

 uniting its multitudinous fragments into the handsome and instruc- 

 tive remains of a right lower jaw exhibited. 



The fossil is 13 inches long, and absolutely free from matrix, so 

 that every aspect and its component structures can be studied. It 

 demonstrates that the lower jaw does not consist of articular, angu- 

 lar, and dentary elements only, as generally described, from which 

 it is evident that the jaw is not constructed according to the Batra- 

 chian type. In addition to those three bones, there are certainly 

 separate splenial and surangular elements, and not improbably a 

 separate coronoid bone also. These five or six bones in each ramus 

 are arranged so as to enclose a deep narrow cavity at least 9 inches 

 long, in the hinder part of the jaw, extending forward from beneath 



