PLATYRRHINA AND CATARRHINA. 



765 



CONTRAST BETWEEN PLATYRRHINA AND CATARRHINA. 



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

 Old World Catarrhina that a two-fold (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 auditory 

 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, wi\h 

 never fewer than 14 verte- 

 bra. 



No cheek pouches. 

 No ischial callosities. 



No sigmoid flexure in the colon 

 descendens. 



Never more than a slight 

 narrowing at the end of the 

 ciTecum, which is usually bent 

 like a hook. 



No hints of a "secondary dis- 

 coidal placenta." 



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. 



A sigmoid flexure. 



The caecum is conical, with a 

 vermiform appendix in Apes. 



A " secondary discoidal placenta " 

 (only hinted at in Anthropoid 

 Apes). 



