358 



OPHIDIA. 



The anterior and middle parts of its walls are formed by descend- 

 ing processes of the parietal and frontal bones (Fig. 197 B), and 

 there is no epipterygoid (columella). The bones of the cranium 

 are firmly and suturally connected and there are no membranous 

 fontanelles ; in these points it resembles the Amphisbaenidae. 

 (2) There are no parotic processes. (3) The basisphenoid is con- 

 tinued forwards as an ossified rostrum (Fig. 197 B}, which pro- 

 bably represents a parasphenoid element, into the ethmoidal 

 region. (4) The nasal region is but slightly ossified, and the 



Etfi 



lo 



Jrt- 



B 



FIG 197 Skull of Tropidonotus natrix ~~< A dorsal, B ventral view (from Wiedersheim) Ag 

 angular, Art articular ; Bp basioccip ital ; Bs basisphenoid ; Ch choanae ; Cocc occipital 

 condyle ; Dl dentary ; Eth ethmoid ; F frontal ; F' postorbital ; Fov fenestra ovaiis 

 foramen for optic nerve ; M maxilla ; N nasal : 01 exoccipital ; Osp supraoccipital ; P pari 

 tal ; Pe periotic ; Pf prefrontal ; PI palatine ; Pmx premaxilla ; Pt pterygoid ; Qu qua< 

 SA suranguar ; Squ squamosal ; Ts transpalatine ; Vo vomer. 



premaxilla is small, unpaired, and only connected with the 

 maxilla by ligament. (5) The temporal arcades are absent : the 

 postfrontal is not directly connected with the squamosal, and 

 there is no jugal or quadrato-jugal ; the geckos and amphis- 

 baenids among lizards present approximations in these respects. 

 (6) The palatines do not unite directly with the vomers or with 

 the base of the skull. They are joined behind to the pterygoids, 

 which are connected with the maxillae by long fcranspalatine 



