DISTRIBUTION.--Forests on the north bank of the Amazons, opposite Olivença, not passing eastwards of Iça on the Iça river. The exact westward extension of this species still remains unknown. The young specimen seen at Fonteboa by Bates, and by him referred to this species, was more probably _B. calvus_, as we know from the account given by Geoffroy St. Hilaire and Castelnau, that the young of _B. rubicundus_ resembles in coloration the adult, and is _not_ paler. HABITS.--Gregarious and diurnal; living in the high trees, and feeding on fruits, probably exclusively, the length of its intestines seeming to indicate that it is more of a vegetarian than its allies. III. THE BALD UAKARÍ. BRACHYURUS CALVUS. _Brachyurus calvus_, Is. Geoffr., C. R., xxiv., p. 576 (1847); id., Arch. Mus., v., p. 560 (1845); Castelnau, Expéd. Amér. Sud, Mammif., p. 17, pl. 4, fig. 1 (1855); W. A. Forbes, P. Z. S., 1880, p. 646; Beddard, P. Z. S., 1887, p. 119, pl. xii. {178}_Ouakaria calva_, Gray, Cat. Monkeys Brit. Mus., p. 62 (1870). _Pithecia calva_, Schl., Mus. Pays Bas, vii., p. 228 (1876). _Pithecia alba_, Schl., t. c. p. 229. (_Plate XVI._) CHARACTERS.--Fur 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. Cæcum 10 inches long along its greater curvature, and not sacculated. According to Mr. Beddard, _B. calvus_ and _B. rubicundus_ 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 Japurá river west of its mouth. This species appears to be confined to the triangle formed by the union of the Japurá 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 Japurá. PLATE XVI. [Illustration: THE BALD UAKARI.]