The cacajao is a curious contrast to the cuxio. It is called also the
black-headed saki. Unlike most of its brethren, it has but a short,
hairy tail, looking as if it had been docked. The head is perfectly
black, somewhat flattened at the temples, with large ears approaching in
shape to those of the human head, and devoid of hair. The fur on the
body is generally of a bright yellowish-brown. When full-grown, the
animal reaches to upwards of twenty inches in length, while the tail is
from three to five inches long. Its legs are covered with rough hair,
and its fingers are unusually long and slender, giving it an awkward
appearance when feeding. In captivity it is a docile and peculiarly
timid animal. A little creature which had been caught exhibited great
alarm at the appearance of several small monkeys of its own country; and
when a serpent was placed before its eyes, it trembled violently.
It is found on the borders of the Negro, where it is known by several
names--among others, as the mono faio, or ugly monkey.