152 LLOYDS NATURAL HISTORY. 



very much ; the posterior lobes of the main brain (or cerebral 

 hemispheres, which are almost always convoluted) are also 

 almost always so large as to entirely cover over the cerebellum 

 (or hind brain), a relation which does not exist between these 

 two regions of the brain in the Leimiroidea. The cerebellum, 

 however, in the Howlers is slightly uncovered. The absolute 

 size of the brain never, in any Ape, approaches that of Man. 

 None of the Cebidce attain the size of even the medium-sized 

 Old World Apes. 



The Cebidce are all arboreal, and strictly confined to the 

 forest regions of Tropical America, from the southern part of 

 Mexico to about the parallel of 30° S. lat. They are divided 

 into four sub-families, namely : The Douroucolis, or Night- 

 Monkeys {Nydipitheciiice) ; the Saki Monkeys {Pitheciince) ; 

 the Howlers {Mycetincey, and the Capuchin Monkeys {CebincB). 



THE NIGHT-MONKEYS. SUB-FAMH.Y 

 NYCTIPITHECIN^. 



The Night-Monkeys are small and elegant animals covered 

 with long hair, and having long bushy tails, which are not 

 prehensile, although they can be curled round a branch of 

 a tree. The caudal vertebrae in these creatures are con- 

 sequently not flattened from above downward, as is the case 

 in the prehensile-tailed groups, but rounded. Their lower in- 

 cisor teeth are set vertically and their thumb is fairly well 

 developed. 



This sub-family contains three genera, the Squirrel-Monkeys 

 {Chrysothrix) ; the Whaiapu-Sais, or Titis {Callithrix) \ and 

 the typical Night-Monkeys, or Douroucolis {NydipitJiecus). 



THE SQUIRREL-MONKEYS. GENUS CHRYSOTHRIX. 

 Chrysothrix^ Kaup., Thierreich., i., p. 51 (1835). 



