VERTEBRATA : MAMMALIA. 777 



face is usually more or less naked, though sometimes whis- 

 kered. The tail is long, and is mostly prehensile ; though in 

 rare instances it is non-prehensile, and has its extremity clothed 

 with hairs. The thumb of the fore-hand may be wanting, and, 

 if present, is not opposable. All the fingers are furnished with 

 flat nails. Their diet is miscellaneous, consisting partly of 

 insects and partly of fruit. 



The Cebida are exclusively confined to the warmer parts of 

 South America, in the vast forests of which they are met with 

 in large troops, climbing amongst the trees. The Spider 

 Monkeys (Ateles), the Howling Monkeys (Mycetes), the " Sapa- 

 jous" or "Capuchins" (Cebus], and the Squirrel Monkey 

 (CaZlithrix), may serve as typical examples of this section of 

 the Quadrumana. In Ateles the tail is long, slender, and 

 powerfully prehensile ; and the limbs are very long and slender. 

 The pollex is absent, or is quite rudimentary. In Mycetes 

 there is a bony drum which is formed by a convexity of the os 

 hyoides and communicates with the larynx. The voice is thus 

 rendered extraordinarily resonant. The pollex is not oppos- 

 able, but is placed on a line with the other fingers. 



In the so-called " Sakis " (PitJieciida) the tail is sometimes 

 long (Pitheaa\ sometimes short (Brachyurus), but is never 

 prehensile, while the lower incisors are inclined forwards. The 

 little "Night-apes" (Nyctipithecus) also have non-prehensile 

 tails, but the lower incisors are vertical, and the eyes, in 

 accordance with the nocturnal habits of the animal, are of 

 immense size. 



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 nostrils looking downwards. 

 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.: 



. 2 2 i i 2 2 3 3 



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



2 2' I I ' 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 

 diastema or interval. The tail is never prehensile, and is 



