QUADRUMANA. 465 



however, those regions of the world have been properly ex- 

 plored in which these forms occur at the present day, we shall 

 doubtless find extinct representatives of this group. The 

 Strepsirhine Monkeys, namely, are at present confined to 

 Madagascar, Western Africa, and the Indian Archipelago ; 

 and these regions are as yet almost unknown, palaeontologi- 

 cally speaking. 



PLATYRHINA. 



The section of the Platyrhine Monkeys is exclusively con- 

 fined to South America, and one of its leading characters is to 

 be found in the almost universal possession of a prehensile 

 tail ; this being an adaptive character by which the animal 

 is suited to the arboreal life which so many of the South 

 American Mammals 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, wide apart, 

 and placed nearly at the extremity of the snout. The prae- 



molars are -^j- in number, and have blunt tubercles. The 



thumbs of the fore-hands are either wanting altogether, or, if 

 present, are not opposable, though versatile. 



The fossil remains of Platyrhine Monkeys are only known 

 to occur in South America, to which country all the existing 

 forms are confined. Here, in deposits of late Tertiary or 

 Post-Tertiary age, have been found remains of Monkeys re- 

 ferable to the existing genera Cebus, Callithrix, and lacchus, 

 along with a large form which constitutes the extinct genus 

 Protopithecus, and which is allied to the recent Mycetes. 



CATARHINA. 



The third and highest section of the Quadrumana is that of 

 the Catarhina or Old World Monkeys. In this section the 

 nostrils are oblique, and are placed close together, and the 

 septum narium is narrow. The thumbs of all the feet are 

 opposable, so that the animal is strictly quadrumanous. In 

 Colobus alone the anterior thumbs (pollex) are wanting. The 

 dental formula is the same as in man, viz. : 



,' ; c 1=1 ; ^ 2 -=?; m *=* - 3 2. 

 22 I I J "22 33 



The incisors, however, are projecting and prominent, and 

 the canines especially in the males are large and pointed. 

 Moreover, the teeth form an uneven series, interrupted by a 



2 G 



