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Page:Popular Science Monthly Volume 4.djvu/487

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in the animate scale; while the star of the resplendent ammonite went down in utter death. And there must have been peculiar conditions of both land and sea, in that Cretaceous day, or those strange reptiles of Brobdingnagian altitude could not walk on the land; nor could their aquatic congeners of cetacean bulk, the huge sea-reptiles, move in their briny homes; so with the Ammonites, and the great selachian fishes. But these—the beauties and the monsters—all died, for there came in new conditions of the land, the sea, and the air.

And with these new conditions came the Eocene age, or dawn of the Tertiary epoch of Earth's lifetime. So decided was this physical change, that all things were ready for its reception of a new race of living creatures. The very surface was newly and lavishly garnished, like a table awaiting the expected guests. And the atmosphere had a balmier vigor, a sort of climatal ripeness, like the aroma of an autumnal orchard whose fruit has matured. Now came the true grasses, and the grains; and the Rosaceæ plants with the strawberry, blackberry, apple, cherry, and plum, etc. And Nature's guests arrived, and entered upon the enjoyment of an unrestrained existence in her grand domain. And they were welcome guests; for leading the train came the (as yet) noblest of her begettings, beings of true mammalian rank. They were of new forms and new appetencies. Some were petite in size, and some were of more than leviathan proportions, and many were bizarre in form; and all were diverse from every thing that had lived before, or that should ever come after. And so each in its own way, as disposition or convenience prompted, enjoyed life. Some preferred the banks of the great rivers, others the grassy meads of the green valleys, and others the sides of the densely-wooded hills. And the timid rodents hid themselves in their burrows at the roar of the carnivores, while both were startled by the beastly bellowing of the great terrestrial behemoths. And these beings, at least some of them, have left their relics in the far West, in places where, until lately, only the red-man had trod.

The geological age just mentioned is called the Tertiary. It was for the first time with true significance sectioned off by Sir Charles Lyell. This learned geologist noticed that this age opened with animal life more like that of the present than any thing that had been before, and that in respect to the molluscs there were many forms identical with existing shells; and he noticed that, as we ascended in this age, the percentage of forms thus similar very rapidly increased. He, therefore, named the bottom section the Eocene, meaning the dawn; and the middle section the Miocene, meaning less of its dawn, that is, farther on in the day; and the highest section he called the Pliocene, meaning still more advanced. To these has been added another, namely, the Pleistocene.

There are three American names which, in respect to the most recent results in vertebrate paleontology, deservedly stand as its