The members of this Sub-family are characterised, externally, by having
elongated slender bodies, with their hind pair of limbs longer than their
front pair, and a very long tail. {84}Internally their digestive organs
differ from those of the _Cercopithecinæ_, the stomach being three times as
large as that organ in any Guenon of the same size. Instead of being a
simple rounded sac, it is elongate and composed of several pouches. These
compartments are quite different, however, from those seen in a Ruminant's
stomach, such as that of the Ox. In the latter, each of the various
divisions is differently constructed, and its mucous membrane is peculiarly
modified; in the Guenon it is divided into two portions, the left of which
forms a very considerable cavity, while the right is long and narrow. Two
great, strong, muscular bands run along its entire length, one along the
greater, the other along the lesser, curvature, like the muscles of the
great intestine, forming a series of large cells. (_Otto._) In addition to
this, the whole organ is twisted upon itself, so that the entrance and exit
regions come to be close together. Its mucous membrane is throughout of the
same character and form. The cæcum has no _appendix vermiformis_, or
worm-shaped tube, which is the representative (as in Man) of the elongate
cæcum found among the Lemuroids, as among most of the Mammals. The muzzle
in this Sub-family is very short, and the nose is generally, but slightly,
prominent. There are ischial callosities, but no cheek-pouches among the
Langurs, though small ones have been described in certain of the Guerezas
(_Colobus_). When laryngeal sacs are present they are formed of a single
sac with a median aperture into the windpipe, in the space below its
superior opening; it may have large prolongations down the front of the
neck, as far indeed as the arm-pits.
The frontal region of the skull is rounded, and the facial angle is
comparatively large. The ascending portion of the hinder part of each half
of the lower jaw is high, and its {85}hindmost molar on each side has five
cusps to its crown. Their breast-bone is very narrow. The vertebræ forming
the tail are much elongated. All have the central (_os centrale_) bone in
the _carpus_ (or wrist).
The posterior lobes of the cerebrum project beyond the cerebellum and
conceal it; they are very short among the Langurs. The principal grooves
and foldings seen in the human brain are represented, and there is a
perfectly distinct _hippocampus minor_--an eminence in the cavity of the
posterior lobe, which was for a long time supposed to be a character
peculiar to the human brain, and the presence or absence of which was once
a celebrated cause of difference between certain distinguished anatomists.
The food of the _Semnopithecinæ_--of which they consume a large bulk at a
time--consists chiefly of leaves and young shoots of trees. For this
purpose their sacculated stomach forms a necessary receptacle and store for
their food during their hasty collection of it.
The Sub-family practically consists of but two genera--_Colobus_ and
_Semnopithecus_. One species, forming a third genus (_Nasalis_), is closely
related to the latter. The _Colobi_ are confined to Africa, and the
_Semnopitheci_--of which there are a large number of species--inhabit the
mainland of India, the Malayan Peninsula, and the neighbouring Archipelago
as far east only as _Wallace's line_, which runs between the islands of
Bali and Lombock, and northwards to the east of Borneo.