_Alouatta seniculus_, Lacép., Mém. de l'Inst., iii., p. 489 (1800). _Stentor ursina_ (nec fig.), Humb. and Bonpl., Obs. Zool., v., p. 354 (1811). _Mycetes seniculus_, Illig., Prod. Syst. Mamm., p. 70 (1811); Geoffr., Cat. Méth. Primates, p. 52 (1851); Schl., Mus. Pays Bas, vii., p. 156 (1876); Gray, Cat. Monkeys Brit. Mus., p. 39 (1870, part.). _Stentor seniculus_, Geoffr., Ann. Mus., xix., p. 108 (1812). _Mycetes stramineus_, Spix, Sim. et Vespert., Bras., p. 45, pl. 31 (1823; nec Geoffr.). _Mycetes chrysurus_, Geoffr., Mém. Mus., xvii., p. 66 (1829). _Mycetes auratus_, Gray, Ann. N. H., xvi., p. 220 (1845); id. Cat. Monkeys Brit. Mus., p. 40 (1870). _Mycetes laniger_, Gray, Ann. N. H., xvi, p. 219 (1845); id. Cat. Monkeys Brit. Mus., p. 40. _Aluatta senicula_, Slack, Proc. Acad. Nat. Sci. Philad., 1862, p. 517. (_Plate XVIII._) CHARACTERS.--Head, neck, limbs and tail, dark chestnut-brown; back and sides golden-yellow; beard in the full-grown male long, the hair golden-yellow at the root, otherwise chestnut-brown; face naked, black; chest naked, the abdomen sparsely covered with long brown hairs. The hair of the body is soft. The tail varies in colour in individual specimens, being sometimes, at its termination, of the same colour as the back, and sometimes bright golden-yellow. The _mammæ_ are occasionally situated in the _axillæ_ (or arm-pits). Length of body, 19½ inches; tail, 20 inches. YOUNG.--Of the same colour as the parents, only a little darker, the hair hard and rigid. {194}DISTRIBUTION.--Brazil; New Granada; Venezuela; Copataza river, Ecuador; Eastern Peru, along the Ucayali and Huallaga rivers.