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82 ZOOLOGICAL GEOGRAPHY. [part hi.
Carnivora. Later, it received its Camelidae, peccaries, mastodons,
and large Carnivora; and later still, just before the Glacial
epoch, its deer, tapir, opossums, antelopes, and horses, the two
latter having since become extinct. All this time its surface
was undergoing important physical changes. What its earlier
condition was we cannot conjecture, but there are clear indica-
tions that it has been broken up into at least three large masses,
and probably a number of smaller ones ; and these have no
doubt undergone successive elevations and subsidences, so as
at one time to reduce their area and separate them still more
widely from each other, and at another period to unite them
into continental masses. The richness and varied development
of the old fauna of South America, as still existing, proves, how-
ever, that the country has always maintained an extensive area
and there is reason to believe that the last great change has
been a long continued and steady increase of its surface,
resulting in the formation of the vast alluvial plains of the
Amazon, Orinoko, and La Plata, and thus greatly favouring
the production of that wealth of specific forms, which dis-
tinguishes South America above all other parts of our globe.
The southern temperate portion of the continent, has probably
had a considerable southward extension in late Tertiary times ;
and this, as well as the comparatively recent elevation of the
Andes, has given rise to some degree of intermixture of two
distinct faunas, with that proper to South Temperate America
itself. The most important of these, is the considerable Austra-
lian element that appears in the insects, and even in the reptiles
and fresh-water fishes, of South Temperate America. These may
be traced to several causes. Icebergs and icefloes, and even
solid fields of ice, may, during the Glacial epoch, have afforded
many opportunities for the passage of the more cold-enduring
groups; while the greater extension of southern lands and
islands during the warm periods—which there is reason to
believe prevailed in the southern as well as in the northern
regions in Miocene times—would afford facilities for the passage
of the reptiles and insects of more temperate zones. That no
actual land-connection occurred, is proved by the total absence