X.] PRIMATES. 139 



edge of the periotic takes place in some of the American 

 Monkeys, as Myceies and Cebiis. 



The suture between the basisphenoid and the pre- 

 sphenoid 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 Mail in many 

 of the smaller American CebidcE 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, 

 and the suture between it and the maxilla is only obliterated 

 in aged specimens. It generally extends upwards on the 

 side of the anterior nares, so far as to meet the nasal and 

 completely exclude the maxilla from taking any part in the 

 boundary of this opening. 



