THE SKULL OF REPTILES 



69 



The temporal fossa, normally (Fig. 55 a) bounded above by the 

 parietal, below by the tabular, squamosal, and postorbital, may be 

 wholly absent, as in the 'Amphisbaenidae (Fig. 56 a), completely 



Fig. 56. Lacertilian skull: A, B, C, y/w/);^w^tf^««, from above, below, and the side. Five 

 halves natural size. D, side view of atlas and axis. 



roofed over by dermal bones, or obliterated by the union of the tem- 

 poral arch with the parietal. 



The premaxillae may be paired or fused; in the mosasaurs (Fig. 

 54 c) the united bone is fused with the nasals posteriorly, or the 

 latter may be absent or vestigial. The lacrimals are always small. 



