776 MANUAL OF ZOOLOGY. 



this being an adaptive character by which they are suited to 

 the arboreal life which so many of the South American Mam- 

 mals are forced to lead. There are neither cheek-pouches nor 

 natal callosities, and there is an additional praemolar, and 

 sometimes a molar less than in Man and the Old World 

 Monkeys. The nostrils are simple, separated by a wide 



septum, and opening laterally. The praemolars are - ----- in 



33 



number and have blunt tubercles. The thumbs of the fore- 

 hands are either wanting altogether, or, if present, are but 

 slightly opposable, though versatile. 



The Platyrhine Monkeys are divided into the two principal 

 sections of the Hapalidce and Cebidce. 



Fam. i. Hapalidce (Arctopitheci). In this family the number 

 of teeth is the same as in the Old World Monkeys and in 

 Man, but there is an additional prsemolar on each side of 

 each jaw, and a molar less. The dental formula of the Mar- 

 moset is 



2 2 i i 3 3 22 



i - - ; c - : pm ; m - = 32. 



22 ' i i ' 3 3 ' 22 



The molars, however, are tuberculate, and though the num- 

 ber of teeth is the same as in the Catarhine Monkeys, in 

 their other characters, the Marmosets are genuine Platyrhines. 

 The hind-feet have an opposable hallux with a flat nail, but all 

 the other toes are unguiculate, and the pollex is not at all 

 opposable. The tail is long and thickly haired, but is not 

 prehensile. 



The Hapalidce are all small monkeys, mostly about as big 

 as Squirrels, and they are exclusively South American, occur- 

 ring especially in Brazil. The best-known species is the com- 

 mon Marmoset (Hapale penicillata\ but several species are 

 domesticated and kept as pets. The genus Midas comprises 

 small Monkeys which differ from the Marmosets chiefly as 

 regards their dentition. 



Fam. 2. Cebidce. In this family are all the typical Platy- 

 rhine Monkeys, in which the dentition differs from that of the 

 Hapalidce, in having an additional molar, so that the molars 

 are the same as in the Catarhina and in Man, but the prse- 

 molars are more numerous. The dental formula is 



/ 2 ~ 2 ; ,532; ^3=3 3_-3 6 . 



22' i I 9 33' 33 



There are neither cheek-pouches nor " callosities ; " and the 



