_Cebus_, Erxleb., Syst. Regne Anim., p. 44 (1777).
This is the typical genus of the American Monkeys. They are distinguished
by having a robust body, covered with woolly fur, with a rounded head and a
face which, instead of having a protruding muzzle, is more erect and
Man-like. They are the commonest Monkeys seen in captivity in our streets.
Their tail is long and covered with hair to the tip, and, though
prehensile, it is not the perfect substitute for an additional hand noticed
in several other genera. Their limbs are only moderately long, and are less
slender than in the Spider-Monkeys. The fore-limbs have a well-developed
thumb, which, as compared with the length of the hand, is the most
{205}Man-like of all the Apes; in some species the nails of the digits are
compressed laterally.
In the skull the cranial portion exceeds the facial. Professor Mivart
observes that in this group the facial part is relatively smaller than in
many of the higher Old-World Apes. The skull has no external bony canal (or
_meatus_) to the ear; and its frontal bones possess large air-cavities. In
the Capuchins the incisor teeth are erect, and are always shorter than the
canines. The molars are four-cusped, and have, on their crowns, two
transverse ridges and the oblique ridge, already described in the
_Lemuroidea_, from the front inner cusp to the hind outer cusp. These
animals have also one milk-molar tooth more than in Man.
The outer surface of the main brain (_cerebrum_) is almost as much
convoluted as in the Old World Apes.
The Capuchins range from Costa Rica to Paraguay, and are represented by
about eighteen species. They are very gentle and docile animals.
F. Cuvier observes in his "Histoire Naturelle des Mammiferes," that of all
the Quadrumana--indeed, of all the Mammals--there are none so difficult to
characterise as the Capuchins of America, whose colours vary almost with
every individual. No two authors agree in the number of species the genus
contains. Brisson recognised three, Linnæus four, Gmelin six, Buffon two,
and George Cuvier supposed it possible that they all belonged to but one
species. Two causes help to produce this diversity of opinion; one is, as
remarked above, the natural disposition which these animals have to vary,
and to become lighter or darker in colour according to circumstances, and
the other is the extremely close relationship that exists between the
different species of the genus. Observations, {206}however, are not yet
numerous enough, nor exact enough, to enable those who have only studied
the species alive in Europe, or had skins, to decide with such imperfect
data as to their sex, age, and habitat. Not until some naturalist has made
a prolonged study of these animals in their native country, and watched
their conduct and relations in the living state, can we hope to attain to
any certain knowledge of how many species the genus contains; and of the
differences between the old and young of both sexes at different periods
from youth to age.