captivity. They are great eaters, and are usually very fat. They are
found only in the far interior of the Amazon valley, and, having a
delicate constitution, seldom live long in Europe. These monkeys are not
so fond of swinging themselves about by their tails as are the spider
monkeys, and offer more opportunities of observing how completely this
organ takes the place of a fifth hand. When walking about a house, or on
the deck of a ship, the partially curled tail is carried in a horizontal
position on the ground, and the moment it touches anything it twists
round it and brings it forward, when, if eatable, it is at once
appropriated; and when fastened up the animal will obtain any food that
may be out of reach of its hands with the greatest facility, picking up
small bits of biscuit, nuts, etc., much as an elephant does with the tip
of his trunk.

We now come to a group of monkeys whose prehensile tail is of a less
perfect character, since it is covered with hair to the tip, and is of
no use to pick up objects. It can, however, curl round a branch, and
serves to steady the animal while sitting or feeding, but is never used
to hang and swing by in the manner so common with the spider monkeys and
their allies. These are rather small-sized animals, with round heads and
with moderately long tails. They are very active and intelligent, their
limbs are not so long as in the preceding group, and though they have
five fingers on each hand and foot, the hands have weak and hardly
opposable thumbs. Some species of these monkeys are often carried about
by itinerant organ men, and are taught to walk erect and perform many
amusing tricks. They form the genus _Cebus_ of naturalists.

The remainder of the American monkeys have non-prehensile tails, like
those of the monkeys of the Eastern hemisphere; but they consist of
several distinct groups, and differ very much in appearance and habits.