Labyrinthodon /rom Warwickshire. 521 



the same species next to be described, and by the fragment of the upper jaw of the 

 second and larger species of Labyrinthodon. The broad palatal plate of the pala- 

 tine bones in the present fossil extends two inches behind the transverse row of 

 teeth, and probably much further in the entire skull ; it is nine lines in breadth 

 anteriorly and six lines in breadth on the inside of the posterior palatal foramen ; 

 the surface next the mouth, which does not support teeth, is smooth and slightly 

 convex. From the curve of the remaining part of the contour of the anterior pa- 

 latal foramen {d, fig. 2. PI. XLIII.), it may be concluded that it was not confluent 

 with its fellow, as in the Crocodiles, or as in the Frog and Menopome, but that the 

 two were distinct as in the Iguana. From the structure of the portion of the nasal 

 cavity preserved in the present fossil, it may be inferred that the Labyrinthodon dif- 

 fered from the Batrachians, and resembled the Saurians in having distinct posterior 

 nasal apertures surrounded by bone, and that its mode of inspiring air was the 

 same as in the higher organized reptiles ; other physiological inductions conse- 

 quent upon this will be noticed in the description of the portion of skull of the 

 larger species of Labyrinthodon ; and I shall conclude the description of the present 

 fossil by again calling attention to the satisfactory proof of its essentially Batra- 

 chian affinities, which the structure of the palate and palatal teeth have yielded. 



Lower Jaw. — ^The next fossil which I proceed to describe, and which, like the 

 preceding one, is from the sandstone in the neighbourhood of Warwick, consists of 

 six inches of the anterior part of the left ramus of the lower jaw (PI. XLIV. figg. 

 8 and 9) ; this ramus is slender, straight, and with its symphysial extremity abruptly 

 bent inwards ; the inner line of the symphysis here forming a regular and deep curve. 

 Its breadth, at the posterior fractured part, is ten lines ; at the anterior part, be- 

 hind the inflected symphysis, seven lines ; the breadth of the anterior fractured 

 portion is one inch. The structure of this long and straight ramus of the jaw pre- 

 sents almost as striking a Batrachian character as any of those derived from the 

 foregoing fossil ; that is to say, the angular piece is of great breadth, extends on 

 both sides of the jaw, and is continued forwards to near the symphysis, forming 

 the whole of the inferior part of the ramus of the jaw, and extending upon the 

 inner as far as upon the outer side of the ramus, the inner plate performing the 

 function of the detached ' os operculare' in the Crocodile's jaw. The dentary piece 

 is supported upon a deep and wide groove along the upper surface of the angular 

 piece, which groove looks obliquely outwards ; the angular piece also projects be- 

 yond the outer edge of the groove, so as to form a strong convex ridge on the 

 external side of the jaw below the dentary piece ; this character, which in the large 

 Bull-frog {Rana pipiens) is confined to the posterior part of the maxillary ramus, is 

 here continued to near the anterior extremity. The teeth in this fragment are long 

 and slender, and so closely correspond in size and shape with those in the upper 



