SKULL 127 



sphenoid, as already mentioned, or may be due to a union of the 

 basal parts of the two orbitosphenoids. Alisphenoids, as well as 

 a basisphenoid, a basioccipital, a supraoccipital, and exoccipitals 

 (often, with par occipital or paramastdd processes) are always present, 

 the paired condyle x being furnished by the exoccipitals (Fig. 92). 



l fenestra 



Fen. cochleas 

 Jug. for. 



Hypoglotial for. 



For. mag. Tect. si/not. 



FIG. 91, B. 



The enlargement of the cranial cavity in correspondence with 

 the increased size of the brain affects the form of the skull in 

 various respects. Thus the supraoccipital becomes shifted 



1 The presence of two condyles appears at first sight to form an important 

 difference to Reptiles, and this is the more remarkable as the occipital region has a 

 similar primary constitution in both groups and differs from that of Amphibians. 

 But in the case of the Sauropsida there are four points of connection between the 

 occipital and the vertebral column. The single condyle is usually formed of 

 three parts (p. Ill), the median or axial of which articulates partly with the 

 centrum proper of the atlas and partly with the odontoid process, with 

 which it is connected by ligament. In Mammals, the lateral articulations 

 are alone developed, and in the Mole embryo there is a single continuous 

 articulation between the skull and vertebral column. 



