CHAP. XVII.] MAMMALIA. I75 



completely covered with hair, although prehensile, and therefore 

 not so perfect a grasping organ. 



Sub-family, Mycetinas, consists of but a single genus, 3fycetcs 

 (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 taU 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, Nyctipithecinse, 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 Chrysothrix (3 sp.), the squirrel-monkeys, are beautiful and 

 active little creatures, found in most of the tropical forests from 

 Costa Pica 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.— HAPALID^. (2 Genera, 32 Species.) 

 General Distribution. 



The Hapalidae, or marmosets, are very small monkeys, which 

 dijffer from the true Cebidse 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 



