_Semnopithecus thomasi_, Collett, P. Z. S., 1892, p. 613, pl. xlii.
DESCRIPTION.--A central occipital crest sloping at first backwards,
reversed on the back of the head, black on the crown; with a lower
indistinct crest on each side of the white forehead. General colour above
dark grey--each hair being partly black and partly white; underneath,
white; a black stripe from the upper jaw to the ear, and a black central
stripe on the forehead; hands and feet black. (_Collett._)
Very old males are darker in colour, with the upper part of the head
brownish-black, the front whitish. Old females are smaller; the young are
silky and nearly white all over.
Closely related and very similar to _S. hosii_, but the cheeks do not form
a connected white area with the white forehead, the space being broken by a
black band from the edge of the mouth to the ear (in the young male and in
the female). In the old male the upper parts of the cheeks are quite black.
Length of body, 24½ inches; tail, about 32 inches.
DISTRIBUTION.--The present species was discovered in the Langkat district
in the North-east of Sumatra, by Mr. Iversen, a Norwegian traveller in that
island, and is named after Mr. Oldfield Thomas, the well-known Mammalogist
of the British Museum.
HABITS.--These Monkeys live in small companies composed of both sexes, in
the highest trees in dry spots of the forest, never descending of their own
accord to the ground, nor {120}visiting the rice-fields, as their food
appears to consist exclusively of fruits. They may be met with, according
to Mr. Iversen, the discoverer of this species, at all seasons of the year
in the same parts of the forest. They hardly ever visit the more open
places, but keep to the highest tree-tops, and make most astonishing leaps
from one branch to another. Those observed were very shy, and, on being
perceived, would seek to hide in the leafy tops of the trees, even leaving
their young exposed on the lower branches. The mother carries her young one
under her belly. The species was often observed in company with the Siamang
(_Hylobates syndactylus_), but not with other Monkeys.