THE OPHIDIA. 



203 



Ophidian and the Lacertilian skull. But there are others, of 

 a less obvious but more remarkable character, by which the 

 skulls of the Ophidian depart not only from that of the Liz- 

 ard, but from that of other Vertehrata. Thus the basi-sphe- 

 noid passes in front of the sella turcica^ into a great rostrum, 

 which extends forward to the ethmoidal region, and probably 

 results from a parasphenoidal ossification. In many adult 



f s.on Ftf P^^^ ^ s^ 



Qu. 



Pmx 



Fr 



vct\ W_Jl^^ so 



Pmx -y-Q 



f iG. 72.— The skull of a Python, viewed from the left side, and in longitudinal section : Ctn, 



stapes ; Tl, tui-binal bone. 



Opliidia two cartilaginous rods lie in grooves on the upper 

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

 while in front they are continued into the cartilaginous ethmoi- 

 dal septum. These rods are the trabeculce, cranii of the foetus, 

 which do not become united in Snakes, as they do in all the 

 other abranchiate Vertehrata. The roof and side-walls of the 

 Ophidian skull are completed in front of the occipital segment, 

 by two pairs of bones, which appear to be parietals and front- 

 als. The " frontal " bones not only completely wall in the 

 sides of the frontal region, but extend inward below", and meet 

 in the middle line, above the basisphenoidal rostrum and the 

 persistent trabeculse. The " parietals " unite suturally with 

 the basisphenoid. These relations are not usual in true front- 

 als or parietals (though the latter unite with the basisphenoid 

 in Ghelonia.^ and the frontals unite in the middle line of the 

 floor of the skull in some Mammals) ; and as there are only 



