x.] PRIMATES. 161 



floccular process of the cerebellum is almost obliterated in 

 the adult Gorilla, Chimpanzee, Orang, and Gibbon, but is 

 persistent and often very large in all other Monkeys. 



A partial ossification of the tentorium from the inner 

 edge of the periotic takes place in some of the American 

 Monkeys, as Mycetes and Cebus. 



The suture between the basisphenoid and the presphenoid 

 remains distinct in the Baboons and all the lower Monkeys, 

 until the animal has nearly attained its full size and acquired 

 its permanent teeth ; but it is completely obliterated, and 

 the cancellous structure of the two bones is continuous, in 

 the Gorilla, Chimpanzee, and Orang, while the animal still 

 retains all its milk-teeth. 



The nasal cavities, with their surrounding bones, are 

 generally longer and of less vertical extent than in Man, 

 but, as in the case of the inclination of the occipital plane, 

 not following any regular serial descent. Thus the propor- 

 tions of these parts are more like those of Man in many 

 of the smaller American Cebida than in the long-faced or 

 " Dog-headed" Baboons (Cynocephali) of the Old World. 



The vomer is generally longer, and of less vertical extent 

 than in Man. The turbinals have much the same general 

 characters, their relative situation of course varying with 

 the elongation, or otherwise, of the nasal passages. The os 

 planum of the ethmoturbinals always forms part of the 

 inner wall of the orbit, having the same relations as in 

 Man. 



The pterygoid plate of the alisphenoid is usually largely 

 developed, and generally projects considerably backwards 

 beyond the pterygoid bone (which is narrow, and has a very 

 distinct hamular process), and there is always a wide and 

 deep fossa between them. 



The premaxilla is always distinct on the facial surface, 



M 



