ghly probable
that the well-known similarities, and no less remarkable differences,
between the present Faunae of India and South Africa have arisen
in some such fashion as the following. Some time during the Miocene
epoch, possibly when the Himalayan chain was elevated, the bottom of
the nummulitic sea was upheaved and converted into dry land, in the
direction of a line extending from Abyssinia to the mouth of the
Ganges. By this means, the Dekhan on the one hand, and South Africa
on the other, became connected with the Miocene dry land and with one
another. The Miocene mammals spread gradually over this intermediate
dry land; and if the condition of its eastern and western ends offered
as wide contrasts as the valleys of the Ganges and Arabia do now, many
forms which made their way into Africa must have been different from
those which reached the Dekhan, while others might pass into both
these sub-provinces.

That there was a continuity of dry land between Europe and North
America during the Miocene epoch, appears to me to be a necessary
consequence of the fact that many genera of terrestrial mammals, such
as _Castor_, _Hystrix_, _Elephas_, _Mastodon_, _Equus_, _Hipparion_,
_Anchitherium_, _Rhinoceros_, _Cervus_, _Amphicyon_, _Hyaenarctos_,
and _Machairodus_, are common to the Miocene formations of the two
areas, and have as yet been found (except perhaps _Anchitherium_) in
no deposit of earlier age. Whether this connection took place by the
east, or by the west, or by both sides of the Old World, there is at
present no certain evidence, and the question is immaterial to the
present argument; but, as there are good grounds for the belief that
the Australian province and the Indian and South-African sub-provinces
were separated by sea from the rest of Arctogaea before the Miocene
epoch, so it has been rendered no less probable, by the investigations
of Mr. Carrick Moore and Professor Duncan, that Austro-Columbia was
separated by sea from North America during a large part of the Miocene
epoch.

It is unfortunate that we have no knowledge of the Miocene mammalian
fauna of the Australian and Austro-Columbian provinces; but, seeing
that not a trace of a Platyrrhine Ape, of a Procyonine Carnivore, of a
characteristically South-American Rodent, of a Sloth, an Armadillo,
or an Ant-eater has yet been found in Miocene deposits of Arctogaea, I
cannot doubt that they already existed in the Miocene Austro-Columbian
province.