oming to land.

The forest-regions of South America offer to animal life so enormous a
mass of foliage that it may not unjustly be termed a sea of verdure, and
creatures there exist which are specially organized for a completely
arboreal life--for never coming to the ground. Such creatures are the
sloths, which pass their lives hanging back-downwards, suspended to the
branches by their huge claws. Thus, they sleep without effort (from the
peculiar mechanism of their limbs), and they move slowly from tree to
tree, having no need to hurry after food, since they live suspended in
the midst of a perennial banquet.

Nearly allied to the sloths were certain huge beasts, now extinct, which
formerly inhabited the same Continent--such as the _Megatherium_ and
_Mylodon_, which rivalled or exceeded our largest rhinoceroses in bulk.
They fed on the same food which nourishes the sloth, but obviously the
branches of no tree could sustain such monsters. They obtained their
leafy pasture, therefore, by a different method. Rearing themselves on
their massive hind legs and powerful tail, as on a tripod, they embraced
the trees with their vigorous arms, and swayed them to and fro, till the
tree embraced was prostrated, and literally fell a prey to their
efforts. These bulky creatures were protected against that danger which
such a mode of life rendered imminent by a specially strong skull
structure, which enabled them to bear a broken head with but little
inconvenience.

In the same region of the earth are found the ant-eaters and armadillos,
and more or less allied to them are the pangolins (_Manis_) of Africa
and Asia. The horny scales which cover the bodies of the last-named
animals caused them for some time to be associated with reptiles rather
than with beasts, though they are true and perfect mammals. Lastly must
be mentioned the aard-vark (_Orycteropus_) of South Africa.

All these creatures, from the sloths to the aard-vark, are commonly
associated together in an order which is termed _Edentata_.

The whole of the orders of mammals yet mentioned agree in certain
important details with respect to their reproductive processes, as well
as in certain smaller anatomical peculiarities, and the whole of the
creatures included within these orders are (and will be) often spoken of
as _Placental Mammals_.

The only beasts which it yet remains to speak of are grouped in two
other orders.

The first of these is called the order _Marsu