236 



THE ANATOMY OP VERTEBEATED ANIMALS. 



These are the most apparent differences between the 

 Ophidian and the Lacertilian skull. But there are others, 

 of a less obvious but more remarkable character, by which 

 the skulls of the Ophidian dej^art not only from that of the 

 Lizard, but from that of other Vertebrata. Thus the basi- 

 sphenoid passes in front of the sella hircica, into a great 

 rostrum, which extends forwards to the ethmoidal region, 

 and probably results from a parasphenoidal ossification. In 

 many adult Ophidia two cartilaginous rods lie in grooves on 



Fig. 



S.On 



pCf I^P Pa FO s„ 



Pmx 



Fr- 



It 17* 



V(^^JLll'° so 



Pmx 



PrOBS 



OliO 



BO 



Fig. 72.— The skull of a Python, viewed from the left side, and in 

 longitudinal section : Cm, stapes ; 2V, turbinal bone. 



the upper face of this rostrum, and pass behind into the 

 basisphenoid, while in front they are continued into the 

 cartilaginous ethmoidal septum. These rods are the tra- 

 beculcB cranii of the foetus, which do not become united in 

 Snakes, as they do in aU the other abranchiate Vertebrata. 

 The roof and side-walls of the Ophidian skull are com- 

 pleted in front of the occipital segment, by two pairs of 

 bones, which appear to be parietals and frontals. The 

 " frontal " bones not only completely wall in the sides of 



