forms and the identity of many of the
species which flourished apparently at the same time in all or in the
most widely separated parts of the world, in the tertiary epoch, on the
contrary, along with the increasing specialization of climates and
their approximation to the present state, we find abundant evidence
of increasing localization of orders, genera, and species; and
this localization strikingly accords with the present geographical
distribution of the same groups of species. Where the imputed
forefathers lived, their relatives and supposed descendants now
flourish. All the actual classes of the animal and vegetable kingdoms
were represented in the tertiary faunas and floras, and in nearly the
same proportions and the same diversities as at present. The faunas of
what is now Europe, Asia, America, and Australia differed from
each other much as they now differ: in fact,--according to Adolphe
Brongniart, whose statements we here condense,[a]--the inhabitants of
these different regions appear for the most part to have acquired,
before the close of the tertiary period, the characters which
essentially distinguish their existing faunas. The eastern continent
had then, as now, its great pachyderms, elephants, rhinoceros, and
hippopotamus; South America its armadillos, sloths, and ant-eaters;
Australia a crowd of marsupials; and the very strange birds of New
Zealand had predecessors of similar strangeness. Everywhere the same
geographical distribution as now, with a difference in the particular
area, as respects the northern portion of the continents, answering to a
warmer climate then than ours, such as allowed species of hippopotamus,
rhinoceros, and elephant to range even to the regions now inhabited
by the reindeer and the musk-ox, and with the serious disturbing
intervention of the glacial period within a comparatively recent time.
Let it be noted, also, that those tertiary species which have continued
with little change down to our days are the marine animals of the
lower grades, especially mollusca. Their low organization, moderate
sensibility, and the simple conditions of an existence in a medium
like the ocean, not subject to great variation and incapable of sudden
change, may well account for their continuance; while, on the other
hand, the more intense, however gradual, climatic vicissitudes on land,
which have driven all tropical and sub-tropical forms out of the higher
latitudes and assigned to them their a