214 LABYRINTHODONTS. 



Avhich was broken across into two nearly equal portions, was the 

 first object of attention. On the inner side of the anterior moiety 

 it appeared to be strengthened by an opercular piece in the form 

 of a thin plate, gradually narrowing to a point, and termiaating 

 at the beginning of the inward curvature of the ramus (tig. 4). 

 Two transverse fractures of this lower jaw display the rela- 

 tions of the external plate of the angular piece with the thin internal 

 bony lamina ; the two pieces are uninterruptedly confluent, and form 

 a single broad and strong piece of bone, supporting the dentary piece 

 upon a groove along its upper surface, and terminating anteriorly 

 at the bend of the expanded premandibular or dentary element, which 

 there receives the extremity of the angular bone in a notch ; the 

 batrachian character is thus as clearly established by the present 

 as by the preceding fragment of the lower jaw. A similar portion 

 of the lower jaw of a Saurian would have exhibited either the dentary 

 element alone, or the anterior extremity of the opercular element in 

 the form of a thin plate applied and limited to the inner side of the 

 dentary piece. The continuation of the angular element alone, forming 

 the lower half of the ramus, to near the symphysis, and supporting 

 the dentary piece in a groove on its upper surface is as striking a 

 Batrachian character in the fossil of the British sandstone, as that 

 observed by Prof. Jaeger in the occipital bone of the great Labyrin- 

 thodon {Salamandroides giganteus) Jaegeri of the German Keuper. 



The smaller serial teeth in the present portion of jaw are about 

 forty in number, and their sockets are in close contact with each 

 other ; they very gradually diminish in size as they approach both 

 ends of the series. Two of the smallest teeth (&') at the anterior part of 

 the jaw are recumbent, in front of the great laniaries ; they may have 

 been incompletely developed teeth of replacement, not yet erected and 

 anchylosed to the bone. 



The alternate sockets are empty in a considerable portion of the 

 posterior part of the series, agreeably with the order of shedding 

 and renovation illustrated in the Labyrinthodon leptognathus, so that 

 the teeth thus appear to be separated by wider intervals than they 

 really are. The form of the teeth is conical, with the base slightly 

 compressed in the direction of the axis of the jaw ; the largest trans- 



