lora and fauna of our
tropical differ from those of our arctic regions.

_In the Tertiary strata._--The tertiary formations were deposited when
the physical geography of the northern hemisphere had been entirely
altered. Large inland lakes had become numerous, as in central France
and other countries. There were gulfs of the sea, into which
considerable rivers emptied themselves, and where strata like those of
the Paris basin were accumulated. There were also formations in
progress, in shallow seas not far from shore, such as are indicated by
portions of the _Faluns_ of the Loire, and the English _Crag_.

The proximity, therefore, of large tracts of dry land to the seas and
lakes then existing, may, in a great measure, explain why the remains of
land animals, so rare in the older strata, are not uncommon in these
more modern deposits. Yet even these have sometimes proved entirely
destitute of mammiferous relics for years after they had become
celebrated for the abundance of their fossil testacea, fish, and
reptiles. Thus the calcaire grossier, a marine limestone of the district
round Paris, had afforded to collectors more than 1100 species of
shells, besides many zoophytes, echinodermata, and the teeth of fish,
before the bones of one or two land quadrupeds were met with in the same
rock. The strata called London and Plastic clay in England have been
studied for more than half a century, and about 400 species of shells,
50 or more of fish, besides several kinds of chelonian and saurian
reptiles, were known before a single mammifer was detected. At length,
in the year 1839, there were found in this formation the remains of a
monkey, an opossum, a bat,[222] and a species of the extinct genus
Hyracotherium, allied to the Peccary or hog tribe.

If we examine the strata above the London clay in England, we first meet
with mammiferous remains in the Isle of Wight, in beds also belonging to
the Eocene epoch, such as the remains of the Palaeotherium,
Anoplotherium, and other extinct quadrupeds, agreeing very closely with
those first found by Cuvier, near Paris, in strata of the same age, and
of similar freshwater origin.

In France we meet with another fauna, both conchological and mammalian
in the Miocene "faluns" of the Loire; above which in the ascending
series in Great Britain we arrive at the coralline crag of Suffolk, a
marine formation which has yielded three or four hundred species of
shells, very different from the