CLASSIFICATION OF MONKEYS 



883 



big toe (or hallux) is opposable except in man ; the nails 

 are almost invariably flat, except in marmosets ; the 

 cerebral hemispheres have in most cases numerous con- 

 volutions, and usually cover the cerebellum ; the stomach 

 is simple except in Semnopithecus and its relatives, in which 

 it is sacculated ; there is a caecum which is often large ; 

 there are two mammae on the breast ; the uterus is simple ; 

 the testes lie in a scrotum ; the penis is pendent ; the 

 placenta is metadiscoidal, being developed by the con- 

 centration of the villi from a diffuse area into a wel- 

 defined disc. Most Anthropoidea are arboreal, gregarious, 

 uniparous, and tropical or sub-tropical. 



Contrast between Platyrrhina and Catarrhina 



The New World Platyrrhina are in many ways so different from the 

 Old World Catarrhina that a twofold (diphyletic) origin of the monkey 

 order is not improbable. There are no transitional forms, and the 

 distribution of the extinct representatives corresponds with that of the 

 living forms. 



Platyrrhina 



Broad cartilaginous internarial 

 septum. 



Nostril directed outwards. 



Tympanic bone not more than a 

 ring. No bony external audi- 

 tory meatus. 



Tympanic bulla. 



AUsphenoid usually meets the 

 parietal on the side of the 

 skull, and the orbital plate of 

 the jugal meets the parietal. 



A large orbito-teraporal fora- 

 men. 



Three premolars. 



Tail often prehensile, with 

 never fewer than 14 verte- 

 brae. 



No cheek-pouches. 



No ischial callosities. 



Catarrhina 



Narrow. 



Downwards. 



With a bony external auditory 

 meatus. 



None. 



Frontal usually meets the squa- 

 mosal, and the jugal does not 

 meet the parietal, being 

 hindered by the frontal and 

 alisphenoid. 



SmalH 



Two premolars. 



Tail not prehensile, 

 practically absent. 



sometimes 



Usually present, except in Apes. 



Present, except in Gorilla, Orang, 

 and Chimpanzee. 



