Semnopithecus larvatus, Fischer, Syn. Mamm., p. 16 (1829); Martin, Mammif. An., p. 453, figs. 279, 280-2 (1841).
Rhynchopithecus larvatus, Dahlb., Stud. Zool., p. 93, pl. iv. (1856).
Semnopithecus (Nasalis) larvatus, Anderson, Zool. Res. Exped. Yun-nan, p. 42 (1878; with full synonymy).
Characters.—Face cinnamon-brown; ears blackish, as also the palms and soles; upper surface of the head, neck, back and sides yellowish-brown, conspicuously marked with reddish-brown and white; rump, tail and limbs yellowish-grey; tails of old specimens quite white; sides of face yellow, and a stripe of the same colour on the shoulders. Under surface yellowish-white.
Hair on the head, which is parted down the centre, on the sides of the face, neck and shoulders, long; the chin full-bearded and the tail tufted; ears small; the nose the most conspicuous feature of the face, produced into a proboscis capable of dilatation, with large nostrils opening downwards, separated from each other by a septum of thin cartilage extending to the extremity. In old males the point of the nose reaches quite below the lowest part of the chin; it is pear-shaped, and furrowed down the middle, giving it the appearance of being double tipped; it is widest in the middle of the free portion. The proboscis is fully developed only at an advanced age in both sexes, being much shorter in the young, and turned upwards. Vigors and Horsfield described their N. recurvus from a specimen which appeared to them to be perfectly adult. The forehead is low; the eyes are wide apart, and the neck is short and much dilated from the presence of a very large laryngeal sac. Length of the body, 29½ inches; of the tail, 26 inches.
Female.—Similar to the male, but it is smaller, and wants the greyish rump markings; while the proboscis is somewhat less developed.
Young.—Have the face blackish and the cheeks wrinkled; the back of the head, down to the shoulders and upper part of the fore-limb is dark reddish-brown. "Through a series of changes during which the red-brown of the upper parts first increases in strength, and the grey-brown of the hips and upper side of the tail change to yellowish-white, the adult pelage is reached." (Anderson.)
This extraordinary animal presents all the structural characters of the genus Semnopithecus; but the lower border of the nasal bones, forming the entrance to the nasal chamber, extends considerably below the lower border of the eye-sockets. The facial portion of the skull does not much exceed the brain-case.
The Proboscis Monkey has the sacculated stomach already described in the Langurs.
Distribution.—The Proboscis Monkey is confined to the island of Borneo. Mr. Hornaday found it along the west bank of the Sarawak river, both near the sea and two miles below the town. It occurs also in some abundance on the Batang Lupar river. Mr. Hose says that it is chiefly found near the mouths of the rivers in Southern Sarawak.