THE HOWLERS. 199 
Young.— 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 villosus, Gray, Ann. Nat. Hist., xvi., p. 220 (1845); id. 
Cat Monkeys Brit. Mus:,.p. 42°(1870) ;*Sclater, P. Z. Si. 
1872, p. 5, figs. r and 2; Alston, in Godm. and Salvin, Biol. 
Centr. Amer. Mamm., pp. 3 and 5, pl. i. 
Characters.— Differs from JZ. 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- 
