Look at the genus Lepidotus, again, persisting without a modification of importance from the Liassic to the Eocene formations inclusively.

The genus Equus is represented as far back as the latter part of the Miocene epoch; but in deposits belonging to the middle of that epoch its place is taken by two other genera, Hipparion and Anchitherium; and, in the lowest Miocene and upper Eocene, only the last genus occurs.

Is it not probable then, that, just as in the Miocene epoch, we find an ancestral equine form less modified than Equus, so, if we go back to the Eocene epoch, we shall find some quadruped related to the Anchitherium, as Hipparion is related to Equus, and consequently departing less from the average form?

Another series of closely affiliated forms, though the evidence they afford is perhaps less complete than that of the Equine series, is presented to us by the Dichobune of the Eocene epoch, the Cainotherium of the Miocene, and the Tragulidoe, or so-called "Musk- deer," of the present day.

Now there is every reason to believe, on other grounds, that both Hindostan, south of the Ganges, and Africa, south of the Sahara, were separated by a wide sea from Europe and North Asia during the Middle and Upper Eocene epochs.

Let us now take a step further back in time, and inquire into the relations between the Miocene Fauna and its predecessor of the Upper Eocene formation.

No Australian type of Marsupial has been discovered in the Upper Eocene strata, nor any Edentate mammal.

So far as the Upper Eocene and the Miocene Mammalian Faunae are comparable, their relations are such as in no way to oppose the hypothesis that the older are the progenitors of the more recent forms, while, in some cases, they distinctly favour that hypothesis.

The period in tine and the changes in physical geography represented by the nummulitic deposits are undoubtedly very great, while the remains of Middle Eocene and Older Eocene Mammals are comparatively few.

There is nothing, then, in what is known of the older Eocene mammals of the Arctogaeal province to forbid the supposition that they stood in an ancestral relation to those of the Calcaire Grossier and the Gypsum of the Paris basin, and that our present fauna, therefore, is directly derived from that which already existed in Arctogaea at the commencement of the Tertiary period.

But there is a still more important positive difference, inasmuch as all these Mammalia appear to be Marsupials belonging to Australian groups, and thus appertaining to a different distributional province from the Eocene and Miocene marsupials, which are Austro-Columbian.

This may seem a bold assumption, but it will not appear unwarrantable to those who reflect upon the very small extent of the earth's surface which has hitherto exhibited the remains of the great Mammalian fauna of the Eocene times.

In the paleontology of character, these fears are the deepest strata, the eocene era, so to speak, of the soul.

There must have been miles and miles of oyster-bed at the bottom of that Eocene sea; among the oyster-beds, beds of a peculiar pebble, which we shall see in our gravel-pit.

They are the shingle beaches of the Eocene sea, part of which are preserved under the London clay.

It is for this reason that the London clay is said to be Eocene, that is, the dawn of the new creation.

Driven out of their native chalk, rolled for ages on a sea-beach, they have tried to get a few centuries' sleep in the Eocene sands on the top of the chalk hills behind us, while the London clay was being deposited peacefully in the tropic sea below; and behold, they are swept out, once more, and hurled pell-mell upon the clay, two hundred feet over our heads.

The Condylarthra seem to have gone out of existence before the time of the middle Eocene, but before this they had become separated into the two great divisions of odd-toed and even-toed ungulates, into which all truly hoofed beasts now living fall.

It is highly probable that these three chief types have descended in as many distinct lines from the Creodonta, and that they were differentiated as early as the middle Eocene, but their exact degree of affinity is uncertain; bears and dogs are certainly closer together than either of them are to cats, and it is questionable if otters and weaselsthe Mustelidae, as they are termedand raccoons are really near of kin to bears.

[geological epochs (list, starting at 70,000,000 years bp)] Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Recent.

It is worthy of remark, however, that in the fossil vegetation of the Eocene world these two vegetable tribes are found associated.

Here, if anywhere on the face of the earth, may we form some conception of the state of our planet during the Eocene period, before the world had come under the dominion of the human race.

Fossils of giant penguins of Eocene and Miocene ages show that there has been extremely little development since.

Eocene, / Cretaceous, \ Porites Jurassic, } and Triassic, } Astraeans.

The happy Eocene beheld him not; That cheerful epoch when a morning ramble Among the mammoths, without gun or shot, Must have been such a truly sportive scramble.