THE WOOLLY SPIDERS 43

purely arboreal life, says Mr. Lydekker, ‘it will
easily be seen that the prehensile tail of those species
which possess such an organ must be of great assist-
ance to their owners in travelling from bough to
bough, and thus from tree to tree. Considering, how-
ever, that the species, like the titis, in which the tail
is not prehensile, are equally as arboreal in habits
as those with prehensile tails, it is quite clear that
the latter organ can only be regarded as a kind
of luxury. Indeed, the whole question as to the
reason why some monkeys have long tails, others
short tails, and others, again, no tails at all, is in-
volved in great obscurity.’

There are ten genera of the Cebide—the capu-
chins, Cebus (Cebus is.merely a derivative of the
Greek ebos, meaning a monkey); the - woolly
monkeys, Lagothrix; the woolly spider-monkeys,
Eriodes ; the spider-monkeys, A¢e/es ; the owl-faced
monkeys, Vyctipithecus ; the squirrel-monkeys, Chry-
Sothrix; the titis, Callthrix; the sakis, Pzthecza ;
the uakaris, Uacaria;,and the howlers. The capu-
chins have thickish tails, with no bare patch at the
end of the tail, where it is used for clinging to the
trees ; in fact, if the tail be looked upon as a third
hand, it is in this genus a hand without a palm. In
the woolly monkeys this patch is present, and con-
spicuous owing to the thickness of the fur everywhere
else. The woolly spiders connect them with the
spiders properly so-called. They are of much lighter
build, and have long, narrow tails and rudimentary
thumbs. The spiders live almost all their time in
the trees, but now and then they come to the ground