THE HOWLERS. I99 



Yoimjj.— Black, with the tips of the hairs of the body yellowish- 

 brown ; base of the tail and the surrounding region reddish- 

 brown. 



This species is remarkable for great variation in colour. The 

 young at first sight, as Dr. Slack has pointed out, appear to be 

 of an intense black colour, but upon a closer examination, the 

 hairs, more especially those of the back and sides of the head, are 

 found to be tipped with reddish-brown. As the animal becomes 

 older the black gradually vanishes, a yellowish-brown colour 

 appearing in its place, until in the adult the only remains of 

 the black are to be found in a few annulations in the hairs of 

 the shoulders. 



The skins are an article of commerce, for saddle cloths 

 and saddle coverings. 



Distribution. — The Rio Negro and Upper Amazonia. Mr. 

 Bates remarks that this is the only species seen in this region. 



V. THE GUATEMALAN HOWLER. ALOUATTA VILLOSA. 



Mycetes viliosus, Gray, Ann. Nat. Hist., xvi., p. 220 (1845); id. 

 Cat. Monkeys Brit. Mus., p. 41 (1870); Sclater, P. Z. S., 

 1872, p. 5, figs. I and 2; Alston, in Godm. and Salvin, Biol. 

 Ccntr. Amer. Mamm., pp. 3 and 5, pi. i. 



Characters. — Differs from A. niger by its abundant, long, and 

 soft hairs, which below, towards their bases, show a rufescent 

 tinge, and by the frontal hairs being sometimes directed down- 

 wards at the base, instead of upwards ; hair on cheeks under 

 the ears, brownish. 



Male. — Entirely black. 



Female and Young. — Also quite black, like the adult male in- 



