THE UAKARi MONKEYS. 175 



jaw, is not borne out by their internal anatomy. The caudate 

 lobe of the liver is very large. This character distinguishes 

 the whole of the Cebidce. from the Old World families. 



The Uakarfs are arboreal Monkeys, very gentle and timid. 

 The distribution of the various species is singularly restricted, 

 each being confined to a small and particular district. 



I. THE BLACK-HEADED UAKARI. BRACHYURUS MELANO- 

 CEPHALUS. 



Simia melanocephala (Cacajao), Humboldt, Obs. Zool., p. 317, 



pi. xxix. (1811). 

 Pithecia melanocephala, Geoffr., Ann. Mus., xix., p. 117 



(1812); Schl., Mus. Pays Bas, vii., p. 227 (1876). 

 Brachyurus ouakary, Spix, Sim. et Vespert. Bras., p. 12, pi. 



viii. (1823). 



Ouakaria spixii, Gray, P. Z. S., 1849, p. 10, cum fig. 

 Ouakaria melanocephala, Gray, Cat. Monkeys Brit. Mus., p. 62 



(1870). 

 Brachyurus melanocephalus, W. A. Forbes, P. Z. S., 1880, p. 



645, pi. Ixiii. 



Characters. Head and nude face-black ; back, sides, thighs, 

 upper surface of tail, and outer and inner sides of legs more or 

 less chestnut-brown ; shoulders, arms, hands, feet, and rest of 

 tail, black. Ears large, naked, and similar in form to those 

 in Man. 



Distribution. Confined, so far as at present known, to the 

 forests traversed by the Rio Casiquiare, Rio Negro, and Rio 

 Branco. This is the most northern form of the three species 

 of the genus, and apparently the most widespread also 

 (see map, p. 180). This is doubtless the " black-faced, grey- 

 haired " species, neither white nor red, which Mr. Bates was 



