70 A>"rHBOPOID APES. 



chimpanzee : the jaw-bones are smaller and less 

 compressed in the centre than thej are in the 

 gorilla. 



When we undertake to describe the skull of the 

 chimpanzee in detail, it becomes necessary to consider 

 separately the skulls of aged and young males, and 

 of aged and young females; for in this case also 

 the distinctions of sex and age are Tery evident. 

 On the skull of an aged male chimpanzee the 

 temporal ridges are not much developed on the 

 coronal arch. They meet on this arch from 60 

 to 90 mm. behind the orbits, and form only a 

 small coronal crest. The transverse occipital crest 

 is somewhat developed, and at its point of union 

 with the coronal crest the temporal ridges divide to 

 form its upper edges. This is the case not only 

 with the Bio Quillu skull, from which Fig. 18 is 

 taken, but with that of the so-called troglodyte 

 Tsctego given by Duvemoy.* In some other speci- 

 mens belonging to aged male animals the presence 

 of a coronal crest cannot, howevier, be detected. In 

 these the temporal ridges are very small, and more 

 or les distant from each other. While the trans- 

 verse occipital crest maintains an almost uniform 

 height on the gorilla skull, like a detached ridge, 

 it is only slightly elevated behind in those chim- 

 panzee skulls in which the crest is partially de- 

 veloped. In the gorilla male this ridge divides the 

 squamous occipital portion, which is sometimes 

 bevelled, sometimes slightly convex; in the male 

 chimpanzee this part is more decidedly arched, and 



* Dorenfjj, table tI. Gg. B. 



