SKELETON. 



93 



palatines bear teeth; an epipterygoid is present and the lower margin of the orbit 

 is formed by the maxillary. In the extinct genera the jugal may bound the orbit 

 below (Palaeohatteria), 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 mentioned 

 (p. 88). 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. 



Statements that 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 



FIG. 96. Skull of Gerrhonotus imbricatus, after Siebenrock. For letters see fig. 68. 



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

 ectopterygoid occurs except in the typhlopids and all four occipitalia bound the 

 foramen magnum. 



The chondrocranium of the LIZARDS (fig. 62), 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 are the fusion of exoccipital and opisthotic 

 to form a 'parotic process' which, together with the squamosal, supports the quad- 

 rate. There is a looseness of connexion of the front of the skull with the occipito- 

 sphenoidal portion, these parts moving on each other. The hyoid apparatus 

 bears two cornua which either end freely in the neck or may reach the parotic 

 process. 



In the PYTHONOMORPHS the striking features are the large supratemporal fossae, 

 the quadrate recalling that of chelonians; and the joint in the lower jaw, between 

 dentary and angular regions. 



