178 ALLEN’S NATURALIST’S LIBRARY. 
Ouakaria calva, Gray, Cat. Monkeys Brit. Mus., p. 62 (1870). 
Pithecia calva, Schl., Mus. Pays Bas, vil., p. 228 (1876). 
Pithecia alba, Schl., t. c. p. 229. 
(Plate X VT.) 
Characters.—F ur very long, straight, and shining from neck to 
tail. Face scarlet ; top of head nearly bald, greyish, passing into 
brown anteriorly and at the sides, with bushy sandy whiskers 
meeting below the chin; throat dark brown, mixed with numerous 
black hairs, the general tint being rich chestnut-brown ; back 
whitish-grey, with black hairs mixed with white ones, which are 
in greater number. Under surface fulvous brown, darker on the 
breast, where brown hairs are numerous; the same brown 
tinge is visible on the arms, legs, the hinder region of the 
thighs, at the wrist, and ankle, and especially on the tail; eyes 
reddish-yellow. Length, 18 inches. 
Some species are paler than the above description, being 
pale sandy-white, slightly rufous below and on the inside of the 
limbs. 
Czecum 1o inches long along its greater curvature, and not 
sacculated. 
According to Mr. Beddard, 4. calvus end B. rubtcundus 
agree very closely in external and in internal characters, while 
B. melanocephalus differs more in external characters from the 
other two than they do from each other. 
Distribution—Opposite Fonteboa ; banks of the Japura river 
west of its mouth. This species appears to be confined to the 
triangle formed by the union of the Japura river and the 
Amazon. It does not pass east of Ega, nor does it cross to the 
south of the Amazon, but keeps to the forests of the low lands 
to the north of that boundary and south of the Japura. 
