The important order of the Elephants (Proboscidea) is also not known to have come into existence during the Eocene period.  On the other hand, the great order of the Beasts of Prey (Carnivora) is represented in Eocene strata by several forms belonging to different types.  Thus the Ardocyon presents us with an Eocene Carnivore more or less closely allied to the existing Racoons; the Paloeonyctis appears to be related to the recent Civet-cats; the genus Hyoenodon is in some respects comparable to the living Hyaenas; and the Canis Parisiensis of the gypsum-bearing beds of Montmartre may perhaps be allied to the Foxes.

[Illustration:  Fig. 233.—­Portion of the skeleton of Vespertilio Parisienis.  Eocene Tertiary, France.]

The order of the Bats (Cheiroptera) is represented in Eocene strata of the Paris basin (Gypseous series of Montmartre) by the Vespertilio Parisiensis (fig. 233), an insect-eating Bat very similar to some of the existing European forms.  Lastly, the Eocene deposits have yielded more or less satisfactory evidence of the existence in Europe at this period of examples of the orders of the Gnawing Mammals (Rodentia), the Insect-eating Mammals (Insectivora), and the Monkeys (Quadrumana).[24]

[Footnote 24:  A short list of the more important works relating to the Eocene rocks and fossils will be given after all the Tertiary deposits have been treated of.]

CHAPTER XIX.

THE MIOCENE PERIOD.

The Miocene rocks comprise those Tertiary deposits which contain less than about 35 per cent of existing species of shells (Mollusca), and more than 5 per cent—­or those deposits in which the proportion of living shells is less than of extinct species.  They are divisible into a Lower Miocene (Oligocene) and an Upper Miocene series.

In Britain, the Miocene rocks are very poorly developed, one of their leading developments being at Bovey Tracy in Devonshire, where there occur sands, clays, and beds of lignite or imperfect coal.  These strata contain numerous plants, amongst which are Vines, Figs, the Cinnamon-tree, Palms, and many Conifers, especially those belonging to the genus Sequoia (the “Red-Foods").  These Bovey Tracy lignites are of Lower Miocene age, and they are lacustrine in origin.  Also of Lower Miocene age are the so-called “Hempstead Beds” of Yarmouth in the Isle of Wight.  These attain a thickness of less than 200 feet, and are shown by their numerous fossils to be principally a true marine formation.  Lastly, the Duke of Argyll, in 1851, showed that there existed at Ardtun, in the island of Mull, certain Tertiary strata containing numerous remains of plants; and these also are now regarded as belonging to the Lower Miocene.