CHAP. XVII.] 
mammalia; 
175 
completely covered with hair, although prehensile, and therefore 
not so perfect a grasping organ. 
Sub-family, Mycetinae, consists of hut a single genus, Mycetes 
(10 sp.), the howling monkeys, characterized by having a hollow 
bony vessel in the throat formed by an enlargement of the hyoid 
bone, which enables them to produce a wonderful howling 
noise. They are large, heavy animals, with a powerful and 
perfect prehensile tail. They range from East Guatemala to 
Paraguay. (Plate XIV., vol. ii,, p. 24.) 
Sub-family, Pitheciinse, the sakis, have a non-prehensile 
bushy tail. Pithecia (7 sp.), has the tail of moderate length ; 
while Brachiurus (5 sp.) has it very short. Both appear to be 
restricted to the great equatorial forests of South America. 
Sub-family, Nyctipithecinae, are small and elegant monkeys, 
with long, hairy, non-prehensile tails. Nyctipithecus (5 sp.), the 
night-monkeys or douroucoulis, have large eyes, nocturnal 
habits, and are somewhat lemurine in their appearance. They 
range from Nicaragua to the Amazon and eastern Peru. Saimiris 
or Cfo'ysothrix (3 sp.), the squirrel-monkeys, are beautiful and 
active little creatures, found in most of the tropical forests from 
Costa Eica to Brazil and Bolivia. Callithrix (11 sp.), are some- 
what intermediate between the last two genera, and are found 
all over South America from Panama to the southern limits of 
the great forests. 
Family 5. — HAPALIIXE. (2 Genera, 32 Species.) 
General Distribution, 
Neotropical, 
Sub-regions. 
N EARCTIC 
Sub-regions. 
Palaiarctic 
Sub-regions. 
Ethiopian 
Sub-regions. 
Oriental 
Sub-regions. 
Australian 
Sub-regions. 
— 2 
The Ilapalidse, or marmosets, are very small monkeys, which 
differ from the true Cebidao in the absence of one premolar tooth, 
while they possess the additional molar tooth; so that while 
they have the same number of teeth (thirty-two) as the Old 
World monkeys, they differ from them even more than do the 
