Hylobates lar, Illig., Abhandl. Akad. Berl., p. 88 (1815); Martin, Mammif. Anim., pp. 416, 433 (1841); Blyth, J. A. S. Beng., x., p. 838 (1841); Gray, Cat. Monkeys Brit. Mus., p. 10 (1870); Scl., P. Z. S., 1870, p. 86, pl. v.; Schlegel, Mus. Pays-Bas, vii., p. 15 (1876); Anders., Zool. Res. Exped. Yun-nan, p. 5 (1878; with full synonymy); Blanford, Faun. Brit. Ind., Mamm., p. 7 (1891).
Hylobates variegatus, Kuhl, Beitr. Zool., p. 5 (1820; young); Desmar., Mamm., p. 51 (1820); Is. Geoffr., Zool. Bélang. Voy., p. 27 (1834).
Simia albimana, Vig. et Horsf., Zool. Journ., iv., p. 107 (1828).
Simia variegatus, Fischer, Syn. Mamm., p. 11 (1829).
Hylobates albimanus, Is. Geoffr., Zool. Bélang. Voy., p. 29 (1834).
Hylobates entelloides, Is. Geoffr., C. R., xv., p. 717 (1842).
Hylobates leuciscus, Cantor, Ann. and Mag. N. H., xvii., p. 338 (1846).
Characters.—Male.—Everywhere deep black, except the face, which is reddish-brown, with the thick hair round it light grey or white, and the hands and feet, which are pale yellow or white; superciliary ridges, whiskers and beard, white. The hair on the fore-arm is nearly erect, with only a very slight forward inclination. The species is subject to great variation, and may be of all shades, from deep black to entirely whitish-yellow (H. entelloides).
Head round; the eyes large; the cheeks flat and depressed; the nose slightly projecting, its tip furrowed, and its nostrils small and converging; the upper lip is divided in the centre by a vertical furrow. In very young individuals the top of the ear is markedly pointed.
Skull with the orbital ridges larger, the muzzle shorter, and the teeth smaller than in H. hoolock; the second and third toes sometimes united by a membrane.