idas or Marmosets--which are again separated into thirteen genera,
consisting of about eighty-six species, greatly diversified among
themselves. In America neither Pithecidae or Lemurs are found: they
exclusively inhabit the Old World.

The Cebidae have thirty-six teeth; the Marmosets possess but thirty-two:
three of them, however, are pre-molar, as are three of those of the
Cebidae, thus distinguishing them both from all the forms of the Old
World.

The Marmosets are a low type of apes--their brain being smooth, and they
having claws instead of nails; but from their intelligent-looking
countenances, and their gentle, playful disposition, they appear to have
as much sense as the larger apes.

The American monkeys differ greatly in size and form. The largest--the
savage black howler--is nearly two feet and a half in length of trunk;
while the beautiful timid marmoset is so small that it may be inclosed
in the two hands. Some have tails twice the length of their bodies; the
caudal appendages of others appear to have been docked, or are
altogether absent. The long tails of some are prehensile, and have a
smooth surface, which enables them to employ it as a fifth hand; others
are covered with thick bushy hair, and are employed apparently only in
balancing the animal. When night comes they roll themselves into a
ball, huddled together as close as may be, to keep themselves warm.
Sometimes it happens that a few little monkeys have not been alert
enough to get into the ball, and are left shivering outside. They keep
up a pitiful howling the whole night through.

One family--the Marmosets--have, as has been remarked, claws instead of
nails. Others are covered with short, coarse hair; while others, again,
have coats of a long, soft silky texture.

Some sport among the branches, seeking their food in the daytime;
others, again, only come forth from the hollows of trees, where they
have their beds during the night season--their eyes being formed, like
those of owls, incapable of meeting the glare of day.

It is remarkable that the smallest of all--the Hapali pygmaeus,
measuring only seven inches in length of body--is among the most widely
dispersed, having found its way into Mexico: the only monkey known to
have wandered far from the great river-plain.

All the monkeys of the New World are arborial; as, indeed, are many of
the animals which, in other parts of the world, live entirely on the
ground. They are mostly