20 
UPPER MAMMAL GALLERY. 
( 90 ), and the eastern P. anvUs ( 80 ) being well-known species. 
In the Arabian P. liamadryas ( 86 ) there is a large mantle o£ 
long hair on the shoulders, which is also developed in the closely- 
allied Abyssinian Gelada, Therojntliecus gelada ( 78 ). 
[Cases 7, The American Monkeys, forming the family Cehidce, usually 
^ ^-] have a dental formula, I. |, C. }, P. |, M. | x 2 = 36, differing 
from that of Old-World Monkeys by the presence of an 
additional premolar on both sides of each jaw. Externally they 
are characterised by their widely separated nostrils and im- 
perfectly opposable thumbs, and usually by their prehensile tails. 
The Cehidce comprise, firstly, the Spider-Monkeys, Ateles 
(Nos. 96 to 110 ), remarkable for their extremely long and 
slender limbs — of which, alone among the familj^ the anterior 
are longer than the posterior, — their rudimentary thumbs, and 
long prehensile tails. The Howling Monkeys, Alouatta or Mycetes 
(Nos. 128 - 131 ), the males of which possess most extraordinary 
voices, the resonance of which is increased by a peculiar 
chamber formed by the middle portion of the bone of the tongue ; 
they are stout, thick-set animals, with well-developed thumbs, 
prehensile tails, and generally of a uniform red, brown, or 
blackish colour, the males being furnished with short thick 
beards. The Woolly Monkeys, Lagothrix (Nos. 114 & 115 ). 
The Saids and Uakaris {Pitliecia^ Nos. .136-140, and Oiiacaria^ 
Nos. 134 & 135 ), two closely-allied genera, the first with 
peculiarly long thick hair all over the body and tail, the latter, 
though long, not being prehensile. The second genus is 
distinguished from all other American Monkeys by having 
scarcely any tail; one species [0. calm, 135 ) exhibited is quite 
l)ald, and all are very thinly haired, in marked contrast to the 
Sakis. The Douroucoulis and Squirrel-Monkeys, Nyctipithecvs 
(Nos. 152 - 154 ), CallitJirix or Callicehus (Nos. 146 - 151 ), and 
Clirysotlirix (Nos. 143 - 145 ) are beautiful little creatures, with 
soft bright-coloured fur, long, hairy, non-prehensile tails, and 
well-developed thumbs ; they live partly on insects. The 
Sapajous, or Capuchin Monkeys, Cebus (Nos. 1 17 - 124 ), form a 
genus of numerous dull -coloured species, with thick prehensile 
tails and well-developed thumbs. Being comparatively hardy 
