SKELETON 



lOI 



fosss, the infratemporal arcade being osseous as in no lizard. Then the quad- 

 rate is anchylosed to pterygoid, squamosal and quadratojugal. Premaxillae, 

 maxillae and palatines bear teeth; an epipterygoid is present and the lower 

 margin of the orbit is formed by the maxillary. In the extinct genera the zygo- 

 matic may bound the orbit below {Palaeokatteria) , and the vomer may bear 

 teeth. 



Dinosaurs have both supra- and infratemporal fossae and frequently a pre- 

 orbital vacuity as well. The rostral and predentary bones have been men- 

 tioned (p. 96). The palatal region recalls that of Sphenodon, except that the 

 teeth, in grooves or sockets, never occur on the palatines. There are such 

 variations in the skulls that few general statements can be made. 



Fig. 105. — Skull of Gerrhonolus imbricatus, after Siebenrock. bo, basioccipital; bs, 

 basisphenoid; eo, exoccipital; /, frontal; mx, maxillary; n, nasal; />, parietal; pf, post- 

 frontal; pi, palatine; pm, pmx, premaxillary; prf, prefrontal; pi, pterygoid; q, quadrate; 

 gj, quadratojugal; sbo, sudocular; so, supraoccipital; spt, supra temporal; sq, squamosal; 

 Ir, transversum; v, vomer. 



Statements which will apply to all Squamata are few. Except in chamaeleons 

 the quadrate is movable, a quadratojugal is lacking, the boundary of the infra- 

 temporal fossa being completed by ligament. The external nares are separate, 

 there are large vacuities in the floor of the skull and the choanae are forward. 

 .\n ectopterygoid occurs except in the typhlopids and all four occipitalia bound 



foramen magnum. 



The chondrocranium of the Lizards (fig. 70), while much like the general 

 type of tropibasic, is very light and is fenestrated to an extent not seen in the 

 ichthyopsids. Among the peculiarities of the adult skull (fig. 105) are the fusion 

 of exoccipital and opisthotic to form a 'parotic process' which, together with the 

 •quamosal, supports the quadrate. There is a looseness of connexion of the 

 front of the skull with the occipiio-sphenoidal portion, these parts moving on 



