THE SKELETON IN MAMMALIA. THE SKULL. 483 



the sphenoid bone. The roof of the skull is partly formed 

 by the large supra-occipital and frontals, but mainly by the 

 parietals (fig. 99, 1), which in Man are of enormous extent. 



In Man and in most monkeys, at any rate when young 

 (fig. 99, B), the roof of the skull is smooth and rounded, but 

 in many forms, such as the Baboons, in the adult the supra- 

 orbital and occipital ridges are much developed. In the Gorilla 

 this is also the case with the sagittal crest (fig. 99, A, 2). The 



FIG. 99. HALF FRONT VIEW OF THE SKULLS, A OF AN OLD, B OF A 

 YOUNG GORILLA (Gorilla savagei) x. (Camb. Mus.) 



1. parietal. 5. squamosal. 



2. sagittal crest. 6. maxilla. 



3. frontal. 7. external auditory meatus. 



4. supra-orbital ridge. 



bones of the upper surface of the cranium interlock with wavy 

 outlines. The nasals vary much in length, being much shorter 

 in man than in most monkeys ; they commonly become early 

 fused together, as do also the frontals. The vomer is well 

 developed, and the ethmo-turbinal always forms part of the 

 boundary of the orbit. There are frequently, as in many 

 Lemuroidea, a pair of more or less well-marked ridges, cross- 

 ing the roof of the skull from the postorbital processes of the 



312 



