174 ALLEN’S NATURALIST’S LIBRARY. 
section, the Sakis (Prthecia). ‘Their various species are re- 
stricted to the great equatorial forests of South America. 
THE UAKARI MONKEYS. GENUS BRACHYURUS. 
Brachyurus, Spix, Sim. et Vespert. Bras., p: 11 (1823); W. A. 
Forbes, PZ, 5., 1880, p. 644. 
Ouakaria, Gray, P. Z. S., 1849, p. 9. 
The species of this genus are at once recognised by their 
short tail, being the only American Monkeys in which this 
organ is short. The fur is short and silky ; the face short, and 
often brightly coloured. The mamme are situated on the 
breast. In the skull the lower jaw is dilated behind, and 
certain bones, the parietal and the malar, are in contact with 
each other for a more or less considerable extent on the side 
walls of the skull. (Cf. W. A. Forbes, P. Z. S., 1880, p. 639, 
figs. 5 and 6.) In Old World Monkeys this contact sever 
(except slightly in Aylobares) takes place. ‘This is a useful 
mark for discriminating between the skulls of New and Old 
World Monkeys. (/orées.) The shortness of the tail is due, 
not toareduction in the number of the vertebrae, which may be 
15 to 17, but in their size. 
In the brain the cerebrum exhibits the more important 
grooves characterising the brain of the higher Apes (Szmzzd@) 
well developed ; the cerebellum (or hind brain) is also well 
developed. Thus in its general characters the brain of the 
Uakaris approaches most nearly to that of the genera Cebus 
and Pithecia (next to be described). By reason of its greater | 
complication and development, it departs widely from that of 
the Titis (Cal/ithrix) and the Squirrel-Monkeys (Chrysothrix). 
A relationship to the Howlers (JAZycetes), suggested by the 
external appearance of the Uakaris and the form of their lower 
