562 THE SAKIS CHAP. 
traversed by the Rio Negro; the Bald-headed Ouakari appears 
to be confined to the triangle formed by the union of the 
Amazon with another affluent, the Japura; and the Red Ouakari 
to the forests on the north bank of the Amazon opposite Olivenca, 
and lying between the main stream and the River Ica. Each of 
them evidently takes the place of the others in its particular 
district. Of this peculiar kind of distribution few instances are 
known amongst mammals, but many somewhat similar cases have 
been observed in birds, reptiles, and insects.” 
The genus Pithecia, the Sakis, consists of five species with 
long bushy tails, which are non-prehensile. They are bearded 
and have a thumb. Like the last genus, Pithecua does not 
extend into Central America. The incisors project forwards, and 
the lower jaw is deep, though the howling apparatus of J/ycetes 
is wanting. The thin, closely-set, and projecting incisors are very 
suggestive of those of the Lemurs. Srachyurus is much like 
Pithecia in this respect, and both differ markedly from such a 
genus as Cebus, where the lower incisors are vertical. An 
anatomical peculiarity of Pithecia is the breadth of the ribs. 
P. satanas is perhaps the best-known species, but all five have 
been exhibited at the Zoological Society's Gardens. As its 
name suggests, P. satanas is entirely black; it shows a curious 
point of difference from -P. chevropotes m1 its way of drinking. 
The latter species, as its name denotes, uses its hand to drink, 
while P. satanas puts its mouth to the water. P. albinasa is 
black with a red patch on the nose, within which again is a 
small white patch. 
troup IL CATARRHINA. 
The Catarrhine Apes are divisible into three or perhaps only 
two families, the Cercopithecidae and the Simudae, to which 
must be added the Hominidae. The Simiidae are sometimes 
spoken of as the Anthropoid Apes. 
Fam. 1. Cercopithecidae.—Of the Cercopithecidae there are 
eight genera (perhaps nine) to be recognised, which may be dis- 
tributed into two sub-families. The first of these two sub-families, 
that of the Cercopithecinae, has the following characters :—There 
are cheek pouches in which the animals store food temporarily. 
