FOSSIL REPTILES. 287 



There is found in this place, between the occipital and the 

 mastoid, and above the tympanic bone, a very small osseous 

 piece distinct from all the others, and which is a sort of epi- 

 physis, or inter-articulary bone for the os tympani. This last, 

 suspended to a pedicle, to which, as we have already seen, five 

 bones contribute, is prismatic, almost straight, and slightly hol- 

 lowed into a semi-canal at its external face. It only supplies 

 the anterior paries of the cavity. The tympanum behind is 

 extended only on membranous parts, and when the throat is 

 opened and the pterygoidean muscles a little removed, the tym- 

 panic cavity appears as a simple hollowing in the roof of the 

 pharynx. 



The floor of the cranium on the sphenoid and basilary bones 

 is concave ; the foss of the pituitary gland is very large, and se- 

 parated almost horizontally from that of the cerebrum by a 

 projecting lamina of the sphenoid. 



The palatines are short, concave in front to conduct to the 

 back nostrils, uniting to the vomer, the anterior frontals, the 

 maxillaries, the transverse, and pterygoidean bones ; not leav- 

 ing there a large empty space, but forming, as usual, a part of 

 the floor of the orbit. They are, each of them, pieced with a 

 small hole analogous to the pterygo-palatine. 



The palatines are continued by the pterygoidean bones. 

 These remaining considerably separated from each other, and 

 becoming vertical, are supported in passing, on the lateral apo- 

 physis of the sphenoid, and proceed to their termination in a 

 point near the internal lower edge of the tympanic bone. They 

 present on their external side an apophysis for their articulation 

 with the transverse bone, which is short and broad, and unites 

 the pterygoid to the palatine, the maxillary and the jugal on 

 each side, leaving between itself the pterygoid, and the palatine, 

 an oval foramen tolerably large, though much less so in propor- 

 tion than in the crocodile. 



That particular, straight, and narrow bone already men- 

 tioned, called the columella^ is articulated on the pterygoidean 



