_Colobus_, Illiger, Prodr. Syst. Mamm., p. 69 (1811).
The Guerezas are a group of Monkeys entirely confined to the African
continent. The character which especially {86}distinguishes them from the
Langurs, which (with the exception of the monotypic Nosed Monkeys of
Borneo) form the remaining members of the Sub-family, is the condition of
their thumbs. In these animals the thumb is practically absent, being
either quite invisible externally, or presenting merely a tubercle, which
may or may not have a nail upon it. The hands are long and straight, and
the nails of the fingers are compressed and pointed. In these animals the
body is slender, though somewhat more robust than in _Semnopithecus_. The
face is naked or covered only with a sparse and soft down, the nostrils
being separated by a wide division. From this feature these Monkeys have
been described by some naturalists as Platyrrhine or Megarrhine. The ears
are rounded above, with the posterior upper angle pointed or square, and
generally naked, but they are sometimes haired or tufted inside. All the
Guerezas have a specially elongated tail, which is often tufted at the end.
Their fur is long and slightly harsher than that of the Langurs, but it is
not ringed with differently coloured bands. Their callosities are large and
naked.
The skulls in _Colobus_ and _Semnopithecus_ are very similar in shape; but
those of the former are often longer, larger, and have a greater cranial
capacity than those of the _Semnopitheci_. The muzzle is short, and the
hind molar of the lower jaw has five tubercles. The thumbs, even when
apparently absent, are represented under the skin by a single bone, the
ungual phalanx, which articulates directly with the metacarpal bone. The
Guerezas differ from the Guenons in having very small cheek-pouches and no
laryngeal sacs. Their stomach is transversely sacculated like the upper
part of the great intestine in the human body.
The Guerezas, which represent the Langurs in Asia, inhabit {87}Tropical
Africa, ranging from Abyssinia and Zanzibar in the east, to Senegambia,
Angola, and perhaps the island of Fernando Po on the west--between about
15° N. lat. on the eastern and 12° on the western side, to 10° S. lat. They
live in small troops in the forest, both on the plains and on the
mountains, their food consisting of fruits, but principally of leaves,
which they eat in large quantities, as the peculiar and capacious form of
their storehouse-like stomach, in lieu of cheek-pouches, would indicate.
Of their habits in their native state very little indeed is known, for they
prefer to keep to the great trees of the forests far from human habitation;
while, owing to their very delicate constitution enabling them to resist
for a very short period the rigours of a climate cooler than their own,
scarcely anything has been learnt of them in captivity. The beautiful skins
of many of the species form a considerable article of commerce in Europe
and America to adorn the costumes of the most refined and cultivated
ladies, who vie for their possession with the semi-nude and barbarous
warriors of Equatorial Africa, by whom they are also used as ornaments for
their persons and for decorations for their weapons.