348 



ZOOLOGY 



SECT. 



In the skull of the Ophidia (Fig. 988) orbitosphenoidal and 

 alisphenoidal elements are absent, their places being taken by 

 downward prolongations of the parietals and frontals. In the 

 substance of the mesethmoid are two cartilaginous tracts (Fig. 

 989, B, T) which are the persistent trabecula^ of the foetal skull. 

 The interorbital septum is absent, and the cranial cavity is 

 prolonged forwards to the ethmoidal region. The palatines 

 (PI) are movably articulated with the base of the skull ; as in 



-Vo 



Fav 



Fio. 



7oo. Skull of Colubrine Snake (TropidonotUS natrix). A, from above ; B, from below. 

 Ag. angular ; Art. articular ; Bp. basioccipital ; B*. basisphenoid ; Ch. internal nares ; Cor.c. 

 occipital condyle ; l)t. dentary ; Eth. ethmoid ; F. frontal ; F. post-orbital ; For. Fen 



jnestra 



occipital condyle ; Dt. dentary, 



ovalis ; M. Maxilla ; N. nasal ; 01. exoccipital ; Osp. f upraoccipital taking the place of 

 orbito-sphenoid ; P. parietal ; Pe. periotic ; P. f. prefrontal ; PL palatine ; Pmx. premaxilla ; 

 Pt. pterygoid ; 01. exoccipital ; Qu. quadrate ; SA. supra-angular ; Squ. squamosal ; 7'x. 

 transverse ; Vo. vorner ; 77, optic foramen. (From Wiedersheim's Comparative Anatomy.) 



the Lizards, they are widely separated from one another, and do 

 not develop palatine plates. They are movably articulated behind 

 withthepterygoids(P), and the latter, through the intermediation 

 of the slender transverse bones (Ts), with the maxillae. The 

 premaxillae are very small (in some venomous Snakes entirely 

 absent), and when present usually fused together. The maxillae (Mx), 

 usually short, articulate by means of a movable hinge-point with 

 the conjoined lacrymal and pre-frontal (La), which, in turn, is 

 movably connected with the frontal. The long and slender quadrate 

 (Qu) is freely articulated with the posterior end of the elongated 

 squamosal. The rami of the mandible, likewise long and slender, 



