HISTORY OF THE PRIMATES 583 



The Anthropoidea are divisible into two sections, the 

 Catarrhina, characteristic of the Old World, and the Platyr- 

 rhina, confined to the New. In the Catarrhina, or Old World 

 apes and monkeys, the dental formula is the same as in Man : 

 i I , Ci,V h m I, X 2 = 32 ; the nostrils are close together and the 

 tympanic bullae have tubular entrances. Many, but not all, 

 have cheek-pouches opening into the mouth. The tail is never 

 prehensile and, except in most of the large, man-like apes 

 (Simiidae), there are naked callosities on the buttocks. With 

 these Old World forms we have no further concern, though 

 it may be noted in passing that Dr. Schlosser has discovered 

 in the Ohgocene of Egypt certain monkeys (\Parapithecus) 

 which he thus describes: ''The number and structure of the 

 teeth, character of the jaws and bodily size make complete 

 the transition from the Anaptomorphids and Tarsiids to the 

 Simiids." 



Section Platyrrhina. South American Monkeys 



In these animals the nostrils are separated by a broad 

 septum, and there are always three premolars above and below 

 (pf). The tail is frequently prehensile and serves as a fifth 

 limb, being capable of supporting the whole weight of the body. 

 There are no cheek-pouches and no callosities, and the tympanic 

 bullae have no bony tubes leading into them. The thumb is 

 but partially, or not at all, opposable and in some genera is absent. 



The New World monkeys are, in general, smaller and lighter 

 than those of the eastern hemisphere ; there are no very large 

 ones and they are all arboreal and are confined to the forested 

 parts of the Neotropical region, except the West Indies, 

 which have none. The marmosets (Hapalidae), the first of the 

 two families into which the Platyrrhina are divided, are little 

 creatures, no longer than squirrels, with long, non-prehensile 

 tails. They are characterized by the dental formula : i |, c \, 

 p I, m I, X2 = 32, and are the only Primates which have no third 

 molar above or below. The thumb is not opposable, though 



