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 fosse 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 Squamara are few. Except in chameleons 
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 
Fic. 96.—Skull of Gerrhonotus imbricatus, after Siebenrock. For letters see fig. 68. 
are large vacuities in the floor of the skull and the choane are forward. An 
ectopterygoid occurs except in the typhlopids and all four occipitalia bound the 
foramen magnum. 
The chondrocranium of the Lizarps (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 PyrHonomorpHs the striking features are the large supratemporal fosse, 
the quadrate recalling that of chelonians; and the joint in the lower jaw, between 
dentary and angular regions. 
