Labyrinthodon /rom Warwickshire. 519 



bones ; in Batrachia, by the palatines and vomer : in all Crocodiles the bones of 

 the palate are edentulous, in all Batrachia they support teeth. There was evidence 

 in the fossil in question of a large laniary tooth projecting from the palatal surface 

 of the mouth, internal to the series of maxillary teeth. I had first to determine 

 whether this was supported, Hke the great laniary teeth of the lower jaw, upon the 

 same bone, viz. the superior maxillary, which supported the serial teeth, or whether 

 it was a true palatal tooth. I am indebted to the skilful sculpturing of Mr. Scharf, 

 spontaneously undertaken by him with a view to render his drawings of the pre- 

 sent fossil more clear and instructive, for the means of determining this question, 

 and for bringing into view some most interesting parts of the cranial anatomy of 

 the Labyrinthodon. The palatal processes of the maxillary bones, instead of extend- 

 ing to the middle line, as in the Crocodiles, are very narrow, as in the Batrachia. 

 The osseous roof of the mouth is principally constituted by a pair of broad and flat 

 bones (PI. XLIII. fig. 2, b), analogous to those which Cuvier describes as a divided 

 vomer in the Batrachia. These bones are, however, of much greater relative ex- 

 tent than in any known Batrachia ; they defend the mouth with a more extensive 

 roof of bone than exists in any lacertine reptile ; physiologically the Labyrinthodon 

 in this part of its structure comes nearest to the Crocodile, but the structure itself, 

 morphologically, is essentially Batrachian ; that is to say, the bony roof of the 

 mouth is formed by a greater development of the vomerine bones, situated, as in 

 the Batrachians, at a part of the skull which is occupied solely by the maxillary 

 bones in the Crocodiles. 



The vomerine bones vary much in their form in the Batrachia ; those of the Me- 

 nopome come nearest in this respect to the Labyrinthodon, especially in the ex- 

 panded anterior extremity of the bone, and it is upon the outer side of this expan- 

 sion that the large tooth just alluded to is situated in the present species of Labyrin- 

 thodon. The corresponding part of the palatal bone in the Menopome and gigantic 

 Salamander supports a transverse row of small teeth ; and the large tooth of the 

 Labyrinthodon is the outermost of a similar transverse row of teeth extending, 

 five in number, across the anterior expansion of each palatine bone, the three 

 median ones being small and equal, the two outermost much larger. In the pre- 

 sent fossil these teeth appear to be alternately shed and reproduced ; that is, the 

 first, third and fifth, counting outwards from the middle line, were in place, the 

 second and fourth being indicated by their empty sockets : this is analogous to the 

 condition of the maxillary series of teeth, and it is an order of shedding and re- 

 newal which is common in many fishes where these processes succeed each other 

 frequently and quickly, and by which the dental series is always kept in an efficient 

 state. The outermost or fifth tooth is placed behind, as well as to the outer side 

 of the socket of the fourth displaced tooth ; and, while it terminates the trans- 



3x2 



