196 ALLEN'S NATURALIST'S LIBRARY. 



Aluatta nigra, Slack, Proc. Acad. Nat. Sci. Philad., 1862, p. 



518- 



Mycetes niger, Thomas, P. Z. S., 1880, p. 394; Schl., Mus 

 Pays Bas, vii., p. 149(1876). 



Characters. Male. Hair rather long and entirely of a deep 

 black ; hair on the back of the head directed forward, meeting 

 at right angles that of the forehead, which is directed backward, 

 forming a well-marked semi-circular ridge. Length, 20 inches ; 

 tail, 17 inches. 



Female and Young. Pale straw-colour washed with black ; 

 the tips of the frontal ridge of hair black ; at birth the young 

 are entirely straw-colour. 



Dr. Slack observes that, in the young, about the period of 

 the second dentition, the hairs upon the mid-line of the back 

 become black at their bases ; soon after, the change takes place 

 upon other parts of the body, the black gradually taking the 

 place of the straw-colour, until the entire body in the adult 

 male is of an intense black colour the adult female having 

 the coloration of the half-grown male. 



Mr. Oldfield Thomas, who examined a specimen collected by 

 Mr. Buckley, in Ecuador, points out that it agreed exactly with 

 Humboldi j original description of the female of his Simla 

 caraya, which he describes as having a black head and back, 

 while the sides and belly are yellow. In all recent descriptions, 

 however, the male is described as being nearly uniformly black, 

 and the female uniformly yellow ; so that Mr. Buckley's speci- 

 men appears to be just such an intermediate specimen as 

 Humboldt described. 



According to Prof. Schlegel, adult males sometimes have the 

 black on the hands and feet mixed with yellow, 



