_Callithrix gigot_, Spix, Sim. et Vespert. Bras., p. 22, pl. 16 (1823);
Schl., Mus. Pays Bas, vii., p. 234 (1876); Weldon, P. Z. S., 1884, p. 6.
_Callithrix gigo_, Gray, Cat. Monkeys Brit. Mus., p. 57 (1870).
CHARACTERS.--Hair about two inches long, soft and slightly woolly over the
trunk; hair on the forehead shorter and more thickly set; that over the
limbs short and loose. General colour of the back reddish-grey behind, more
ashy over the forehead and limbs; the hair black at the base,
cream-coloured further up, the tips ringed with chestnut and black. Muzzle
and chin black, with a few short, strong, white hairs; a black line along
the nose and round the eyes; the eyelids white; the eye-lashes and long
eye-brows black; forehead thickly covered with loose grey hairs, slightly
tipped with black; a faint ridge across the brow between the ears; the ears
black, covered with soft black hairs, except for a small grey tuft at their
hind outer angle. In front of the ears a light grey band over the cheeks,
continued above on to the forehead, below to the chest; throat naked, light
pink; under surface {166}of the limbs pale grey; the hands and feet black;
tail red, the hair bushy at its base. Length of the body, 14 inches; of the
tail, 13½ inches. (_Weldon._)
Cæcum with dilated end; liver more divided than in _C. moloch_; the two
halves (_rami_) of the lower jaw enormously deep, resembling those of the
Howlers (_Mycetes_).
DISTRIBUTION.--Brazil; Bahia, and the country between the Parahyba and the
mountains to the north of the Bay of Rio de Janeiro.
HABITS.--This species is very rare, and nothing is known of its habits.
Professor Weldon writes, in his paper in the "Proceedings of the Zoological
Society," referred to above: "Sir W. Flower has suggested to me that the
enormous depth of the _ramus_ of the mandibles in this _Callithrix_ pointed
to the existence of some arrangement resembling that of _Mycetes_. It was
difficult to determine this point in a young female; but the swollen
condition of the thyroid, together with the existence of a patch of
ossification on each side, seem to show the possible existence of a howling
apparatus in the male."