f Greece), Beavers, Mice, Jerboas, Squirrels, and Marmots. All the
principal living groups of this order were therefore differentiated
in Middle Tertiary times.

The _Cheiroptera_ are represented by small insect-eating Bats;
and the order of the Insectivorous Mammals is represented by
Moles, Shrew-mice, and Hedgehogs.

[Illustration: Fig. 248.--Lower jaw of _Pliopithcus antiquus_.
Upper Miocene, France.]

Lastly, the Monkeys (_Quadrumana_) appear to have existed during
the Miocene period under a variety of forms, remains of these
animals having been found both in Europe and in India; but no member
of this order has as yet been detected in the Miocene Tertiary of
the North American continent. Amongst the Old World Monkeys of
the Miocene, the two most interesting are the _Pliopithecus_
and _Dryopithecus_ of France. The former of these (fig. 248)
is supposed to have been most nearly related to the living
_Semnopitheci_ of Southern Asia, in which case it must have possessed
a long tail. The _Mesopithecus_ of the Upper Miocene of Greece is
also one of the lower Monkeys, as it is most closely allied to
the existing Macaques. On the other hand, the _Dryopithecus_
of the French Upper Miocene is referable to the group of the
"Anthropoid Apes," and is most nearly related to the Gibbons
of the present day, in which the tail is rudimentary and there
are no cheek-pouches. _Dryopithecus_ was, also, of large size,
equalling Man in stature, and apparently living amongst the trees
and feeding upon fruits.

CHAPTER XX.

THE PLIOCENE PERIOD.

The highest division of the Tertiary deposits is termed the
_Pliocene_ formation, in accordance with the classification proposed
by Sir Charles Lyell. The Pliocene formations contain from 40 to
95 per cent of existing species of _Mollusca_, the remainders
belonging to extinct species. They are divided by Sir Charles
Lyell into two divisions, the Older Pliocene and Newer Pliocene.

The Pliocene deposits of Britain occur in Suffolk, and are known
by the name of "Crags," this being a local term used for certain
shelly sands, which are employed in agriculture. Two of these
Crags are referable to the Older Pliocene, viz., the White and
Red Crags,--and one belongs to the Newer Pliocene, viz., the
Norwich Crag.

The _White or Coralline Crag_ of Suffolk is the oldest of the
Pliocene deposits of Britain, and is an exceedingly local formation,
occurring in but a single small area, and having