786 MAMMALIA. 
except in man; the nails are almost invariably flat, except 
in marmosets; the cerebral hemispheres have in most cases 
numerous convolutions, and usually cover the cerebellum ; 
the stomach is simple except in Semnopithecus and its 
relatives, in which it is sacculated ; there is a cecum which is 
often large; there are two mamme 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 concentration of the villi from a diffuse area into a well- 
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. 
Alisphenoid usually meets the 
parietal on the side of the 
skull, and the orbital plate of 
the jugal meets the parietal. 
A large orbito-temporal fora- 
men. 
‘Three premolars. 
Tail often prehensile, with 
never fewer than 14  verte- 
bree, 
No cheek-pouches. 
No ischial callosities. 
CATARRHINA 
Narrow. 
Downwards. 
Forms 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. 
Small. 
Two premolars. 
Tail not prehensile, sometimes 
practically absent. 
Usually present, except in Apes. 
Present, except in Gorilla, Orang, 
and Chimpanzee. 
