PECULIARITIES OF THE SKULL 219 



The skull of the young gorilla is much like that of the 

 chimpanzee and remains so until it approaches the adult 

 state. At this period the ridge above the eyes becomes 

 more prominent, and at the same time a sharp, bony ridge 

 begins to develop along the temples and continues around 

 the back of the head on that part of the skull called the 

 occiput. At this point it is intersected by another ridge 

 at right angles to it. This is called the sagittal ridge. It 

 runs along the top of the head towards the face ; but on 

 the forehead it flattens nearly to the level of the skull and 

 divides into two very low ridges, which turn off to a point 

 above the eyes and merge into that ridge. These form a 

 continuous part of the skull and are not joined to it by 

 sutures. The mesial crest in a very old specimen rises to 

 the height of nearly two inches above the surface of the 

 skull, and imparts to it a fierce and savage aspect ; but in 

 the living animal the crests are not seen, as the depressions 

 between them are filled with large muscles, which make 

 the head look very much larger than it otherwise would. 

 These crests affect only the exterior of the skull and do 

 not appear to alter the form or size of the brain cavity, 

 which is slightly larger in proportion than that of the chim- 

 panzee. These crests are peculiar to the male gorilla. The 

 female skull shows no trace of them. 



There is at least one case in which the male gorilla has 

 failed to develop this crest. In the series of skulls found 

 in the cuts given herewith, No. 6 is that of an adult male 

 gorilla. I know it to be such, for I dissected the animal 

 and prepared the skeleton for preservation. He was killed 

 in the basin of Lake Ferran Vaz, not more than three or 



