38 CEBIB^. 



18. Midas. Head with short hairs. 



19. Seniocebus. Head naked in front, hairy behind. 



Dahlbom arranges the prehensile-tailed monkeys according to 

 their anatomical character, thus : — 



I. Muzzle obtuse, conical ; spinous processes of the lumbar vertebrae 



acutely triangular, directed more forward than the rest, nearly 

 inciuubent. 



a. Eyes very large, lateral ; septum of nose narrow. Nyctipithecus. 



b. Eyes moderate, anterior ; septum of nose broad. Callithrix. 



II. Muzzle bhmt, truncated ; spinous processes of the lumbar vertebree 



trapeziform. 



a. Tail hairy aU over. 



* Septvmi of the orbit membranaceous. Saimiri. 



** Septum of the orbit bony. Cebus. 



h. Tail-end bald. Atehs, Laf/othrix, Mycetes. (Zool. Stud. p. 146.) 



Section A. Gymnura. Tail elongate, prehensile, stronyly revolntc, hairy ; 

 tinder surface of the tip naked, callons. Gritiders f . f . 



Tribe I. MYCETINA. 



Head pjTamidical ; face oblique ; chin and crop gibbous, covered 

 with long rigid hairs. Canines large. Lower jaw much dilated behind. 

 Os hyoides very large, spongy. Thumb distinct. Claws convex. Tail 

 very long. Ferocious, noisy before the rising and after the setting 

 of the sun. Living on leaves of trees. 



1. MYCETES. 



Head pyramidical. Face and the lower part of the body nearly 

 naked. Tail strong. Fingers very long. 



Mycetes, Illiger ; Gray. Ann. Sf May. N. H. 1845, xvi. p. 217. Sten- 

 tor, Geoff. Ahiata, Lacep. Cebus, Er.il. Aluatta, Slack. 



Spix describes the male and the female M. caraya as being black, 

 and the young yellow. Prince Neuwied observes that the males 

 and the specimens of M. ursinus from the more northern region of 

 Brazil are rufous or ferruginous, while the females and those from 

 the more southern regions are bro^vn or blackish brown. Lichten- 

 stein describes the young of this species as blackish. Cuvier observes 

 that there is very little difference between J-/, ursinus and M. senicidus. 

 The specimens of the two sexes that are in the British Museum, 

 received at the same time and fi'om the same locality, are nearly the 

 same colour, and the young and adults equally so ; but some speci- 

 mens of apparently the same species vary considerably in tint ; some 

 of the black species show so many red haii's scattered among their 



