Whilst herbivorous Quadrupeds, as we have seen, were extremely abundant during Miocene times, and often attained gigantic dimensions, Beasts of Prey (Carnivora) were by no means wanting, most of the principal existing families of the order being represented in deposits of this age.  Thus, we find aquatic Carnivores belonging to both the living groups of the Seals and Walruses; true Bears are wanting, but their place is filled by the closely-allied genus Amphicyon, of which various species are known; Weasels and Otters were not unknown, and the Hyoenictis and Iditherium of the Upper Miocene of Greece are apparently intermediate between the Civet-cats and the Hyaenas; whilst the great Cats of subsequent periods are more than adequately represented by the huge “Sabre-toothed Tiger” (Machairodus), with its immense trenchant and serrated canine teeth.

Amongst the Rodent Mammals, the Miocene rocks have yielded remains of Rabbits, Porcupines (such as the Hystrix primigenius of 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.