CEBIDAE. 657 



variable ; in Chrysothrix the cerebrum projects behind the cerebellum, 

 while in Mycetes it barely covers it ; in Cebus and Ateles its surface is 

 much convoluted, in others (e.g. Nyctipithecus} it is almost smooth. 

 They are arboreal animals and confined to the Neotropical region. A 

 few fossil remains of living forms have been found in the Pleistocene of 

 Brazil and a few genera (Homunculus, Anthropops, Pitheculus) have 

 been recorded by Ameghino from the Eocene of Patagonia, the family 

 being unrepresented in the intermediate strata. 



Sub-fam. 1. Mycetinae. Lower incisors vertical, hyoid bones 

 inflated, tail long, prehensile and naked beneath at the end ; pollex 

 well developed. Alouata Lacep. (Mycetes 111.), howling monkeys, 

 face large with a low facial angle, the basicranial axis is as long as 

 the cerebral cavity and the foramen magnum is placed at the hind 

 end of the skull ; the cerebrum is well convoluted, but it hardly 

 covers the cerebellum ; the rami of the mandible are very deep 

 and protect the much swollen body of the hyoid in which is placed 

 a large air sac communicating with the larynx below the epiglottis ; 

 the ventricles of the larynx are also dilated and prolonged upwards. 

 They are in the habit of occasionally sitting on the topmost branches 

 of trees and howling, the resonating apparatus increasing the 

 power of the howls. The use of the howl is not known ; it has 

 been suggested that it is for the purpose of intimidating their 

 enemies ; 6 sp. 



Sub-fam. 2. Pitheciinae. Lower incisors inclined forwards, tail 

 not prehensile, pollex well developed. Pithecia Geoff r., the sakis, 

 with long tail, 5 sp. Brachyurus Spix (Ouacaria Gray), short tail, 

 3 sp., which have a curious and local distribution in the forests on 

 the banks of the Amazon. 



Sub-fam. 3. Nyctipithecinae. Lower incisors vertical, tail long, 

 not prehensile, pollex well developed. Callithrix Geoffr., teetees, 

 about 1 1 species. Chrysothrix Kaup ; squirrel monkey, face small 

 with high facial angle, plane of the foramen magnum horizontal, 

 cerebrum nearly smooth, projecting behind the cerebellum, 3 sp. 

 Nyctipithecus Spix, douroucoulis, nocturnal, with large eyes, with 

 owl-like face, head and brain as in the last ; 5 sp. 



The extinct Eocene genera of Ameghino, Homunculus, Anthro- 

 pops t Pitheculus, Homocentrus, Eudiastatus, are placed in this sub- 

 family. 



Sub-fam. 4. Cebinae. Lower incisors vertical, tail long, pre- 

 hensile, pollex may be absent. Ateles E. Geoffr., spider-monkeys, 

 coaitas, slender, long limbed forms with non-woolly fur, and absent 

 pollex ; tail naked below at the end, very prehensile ; about 1 1 sp. 

 Brachyteles Spix (Eriodes E. Geoffr.), with woolly fur and reduced 

 pollex, tail naked below at the end, nails compressed and pointed ; 

 3 sp. Lagothrix E. Geoffr., barrigudos, woolly monkey, pollex well 

 developed, tail naked below at the end, fur woolly ; 2 sp. Cebus 

 Erxleb., sapajous or capuchins, monkey of organ grinders, not 

 woolly, pollex well developed, tail completely hairy ; about 17 species. 

 The extinct family Nesopithecidae from the Pleistocene of Mada- 

 gascar is placed here. It has also been assigned to the lemurs. The 

 lacrymal foramen is just inside the orbit, and the dentition is 

 * ' T c T P t m f ' * ne m l ars being pithecine, but the tympanic 

 bulla is formed by the periotic as in Madagascar lemurs. 



Z. II U r 



