_Simia satanas_, Hoffm., Mag. Ges. Berl., x., p. 93 (1807); Humb., Obs. Zool., i., p. 314, pl. xxvii. (1811). _Pithecia satanas_, Geoffr., Ann. Mus., xix., p. 115 (1812); Scl., P. Z. S., 1864, p. 712, pl. xli.; id., t. c. p. 138; Schl., Mus. Pays Bas, vii., p. 224 (1876). _Chiropotes cuxio_, Lesson, Sp. Mamm. Bimanes et Quadrum., p. 179 (1840). _Chiropotes ater_, Gray, Cat. Monkeys Brit. Mus., p. 61 (1870). _Chiropotes satanas_, Gray, t. c. p. 61. CHARACTERS.--MALE.--Fur soft; tail bushy and as long as the body; crown with long black hair arranged on each side, divided by a central line. "The hair of the head sits on it like a cap, and looks as if it had been carefully brushed." (_Bates._) Long whiskers on each side, and the chin with a moderate beard. Fur black and shining; back sometimes washed with grey or ashy-brown. FEMALE.--Similar to the male, but having a browner back. YOUNG.--Beard absent or rudimentary; hair of crown radiating from centre and projecting forwards. The skull in this species is sometimes ossified into one piece. DISTRIBUTION.--Lower Amazonia; Para; British Guiana; the River Orinoco, towards the Rio Negro. HABITS.--Little is known of the habits of the Black Saki, which is also known under the names of "Cuxio" and "Mono {187}Capuchino." It lives in the most retired parts of the forest, where the ground below it is not inundated by the river, and feeds on fruits. It is said that this animal--unlike the next species--drinks freely, always bending down on its hands and putting its mouth to the surface of the water, heedless of wetting its beard and indifferent to the observation of onlookers. Sir Robert Porter says that he never saw it take up water in the hollow of its hand, and convey it to its mouth to drink. Its voice is a weak and chirping whistle, which becomes shrill and loud when the animal is angry. A young male of this species, which died in the Zoological Society's Gardens in 1882, presented an abnormal condition. The peculiarity consisted, as Mr. W. A. Forbes, the late distinguished prosector to the Society, has pointed out in the "Proceedings," in the completely "webbed" condition of the third and fourth digits of the manus (hand) on each side, these two fingers being completely connected together, down to their tips, by a fold of nude skin, and with their nails closely apposed, though not connected along their contiguous margins. The other digits of the hands, as well as those of the feet, were quite normal, the webbing not extending beyond the middle of the first phalanx. Mr. Forbes remarks: "The case is interesting, partly as affording an excellent instance of an abnormal condition affecting homologous parts of opposite sides in an exactly similar way, and partly as showing that the lower Primates are subject, occasionally, to a condition of things which, as is well known, also occurs not at all rarely in Man." IV. THE RED-BACKED SAKI. PITHECIA CHIROPOTES.