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THE RECENT.

CAINOZOIC SYSTEMS. THE TERTIARY AND POST-TERTIARY.

HAVING passed the middle ages of the earth's history, whose life-species have all, or nearly all, disappeared, we enter upon an epoch whose forms insensibly graduate into those that are now our fellow-participators in the great progressional scheme of vitality. In other words, we approach the Cainozoic, or "recent-life period," which, though but as yesterday compared with the æons of the paleozoic and mesozoic, yet embraces a vast lapse of time, and is necessarily characterised by higher and still advancing forms. We say necessarily characterised, for though science can prove no causal connection between the physical and vital manifestations of the globe, the one set of changes so invariably accompany the other, that we are compelled to regard them as necessary concomitants. And yet, though concomitants in time, they may stand in no relation to each other as cause and effect, but be each an independent phase of that divine creational plan that is still evolving itself around us. We, who but dimly perceive the broken outline of the scheme, can only note the coincidence; those in after ages of higher intelligence may succeed in tracing the connection. But whatever that connection, it is now more marked and appreciable, and geologists can associate with almost every fluctuation of condition, a change in the accompanying aspects of cainozoic life.

It is now that the more complex forms of an exogenous flora are superadded to the endogens and gymnogens of the mesozoic, and in their more varied forms and higher utilities become not only a fitter ornament for a more varied surface, but a necessary sustenance for a higher and more diversified fauna. The herbs, and shrubs, and trees—the flowers, and fruits, and grains-all that can gladden the senses or satisfy the wants of man and his existing lifecomrades, appear with the current epoch, and by their appearance again confirm that fitness that ever reigns between the organic and inorganic aspects of creation. In the animal world the advance is equally apparent, and in orders where no advance appears a thousand modifications present themselves. Among the protozoans the calcareous sponges for the most part disappear, their place being taken by those of a horny nature, while the foraminifera are culminating in size and complexity of configuration. The encrinites, with one or two solitary exceptions, have vanished from the waters; and the sea-urchins, so exquisitely preserved in the chalk, are reduced by several of their most beautiful and numerous families. Among the shell-fish the brachiopods dwindle to a few families, the true bivalves are still on the increase, the gasteropod univalves become dominant in genera and species, while the shellclad cephalopods that thronged the mesozoic ocean in myriads, perish to a solitary genus. The crustaceans become less natatory and more ambulatory in their character, while the insects, so imperfectly preserved in the past, now throng every elementair, earth, and water-in apparently still increasing numbers. The placoids and ganoids, so long the only representatives of ichthyic life, are now on the wane, and the cycloids and ctenoids appear as the prevailing orders. Of the ichthyosaurs and plesiosaurs that whale-like ruled the ocean, of the megalosaurs and hylæosaurs that

tenanted the plain and roamed the forest, and of the pterosaurs that winged the air, not a living trace remains. They are utterly extinguished, and their place is now filled by the crocodiles, lizards, turtles, and serpents of existing nature. The birds so scantily preserved (though largely indicated) in mesozoic strata, and the mammals represented only by a few insignificant marsupials, now assume the chief importance in the great vital scheme; and last, and highest of all, man himself enters on the stage of being as the crowning form of the current epoch.

To facilitate comparison, it is usual to subdivide the Cainozoic into eocene, miocene, pliocene, and pleistocenethat is, into its earliest, less recent, more recent, and most recent life-stages; but enough for our review to treat it in two great sections-the first, when land and sea had a somewhat different distribution from the present; and the second, when they had assumed, within the limits of an appreciable mutation, their existing arrangement. Adopting the familiar phraseology that designates the palæozoic as primary, and the mesozoic as secondary, we may regard the first section as tertiary, and the second as posttertiary-ever bearing in mind that such distinctions are mere provisional aids to facilitate the comprehension of geological progression. It has been customary, no doubt, for certain geologists, generalising from limited tracts in Europe, to draw a bold line of demarcation between the chalk and tertiary-so bold that not a single species was regarded as passing from the one epoch to the other. This, like many of the early conclusions of the science, is altogether erroneous; and now, even in Europe, to say nothing of America, abundant passage-beds have been detected, showing in this instance, as in every other, that abrupt transitions are at the most merely local and limited pheno

mena. Assuming, then, that the life-forms of the Chalk pass insensibly into those of the Tertiary, even though in many European areas the cretaceous era was suddenly brought to a close by the violent displacement of the then land and sea, we yet discover a wide difference between the vital aspects of these respective epochs. In the northern hemisphere the tertiary seas still trend in an easterly and westerly direction-stretching diagonally through what is now Central Europe and Southern Asia, spreading over a large tract of Northern Africa, and covering in North America wide belts of the Southern States. Shut up from the northern currents that seem to have influenced the chalk seas, and exposed to those which, like the Gulf Stream, partake of a tropical temperature, the climate of the tertiary areas becomes more genial, and is, in the progress of creation, accompanied by a more exuberant flora and fauna. The seas, even in the latitudes of England, teem with southern forms; while the lands, clothed with a vegetation that finds its nearest analogues in the plants of sub-tropical regions, were tenanted by gigantic mammals which, like the elephant, rhinoceros, hippopotamus, tapir, lion, and tiger, now find their headquarters in the forests and plains of the torrid zone. Extensive lacustrine areas also appear in certain regions, as in Central France, and in their freshwater forms present, for the first time, a fauna but doubtfully and obscurely represented in former epochs.* In fine,

* With the exception of the estuarine beds of the Weald, and the doubtfully estuarine portions of the Carboniferous system, we are altogether ignorant of the fresh-water areas of the older epochs. Lake, river, and marsh must have existed then as now, each peopled by its own distinctive tenantry; but of these forms we have not a single trace, and it is only as we approach the Tertiary epoch that a fresh-water fauna becomes known and appreciable. As we cannot believe in the total obliteration of ancient fresh-water deposits, so we hopefully look forward to important discoveries in this rich and varied section of vitality.

we have every type and feature of existing vitality; and the character of the period will perhaps be better indicated by a notice of the forms that have become extinct, than by any description of the whole, which still constitutes in a great measure the flora and fauna now flourishing around us.

Separating the early tertiaries—the eocene and miocenefrom the pliocene and pleistocene, when, under the changing conditions of sea and land, the climate of the northern hemisphere began to assume a boreal character; we shall shortly glance at the more marked and peculiar aspects of this early period. Wherever we turn whether to the clays and gravels of the London basin, or to the marls and gypsums of Paris, whether we restrict our review to the south of Europe, or carry it forward to the centre of Asia-we everywhere find in these earlier tertiaries abundant evidence of a warm - temperate, or even subtropical flora. Palm-like leaves and fruits, such as now flourish on the mud-islands of the Ganges (flabellaria, nipadites, tricarpellites), leguminous seeds of arboreal growth (legumenosites), twigs and leaves of mimosa, laurel, and other plants, whose congeners now find a habitat in southern latitudes, are thickly scattered through these strata. Nor are these the mere twigs and fragments of tropical forests, drifted from afar by gigantic rivers; for associated with the formation. are beds of lignite or wood-coal, composed of kindred plants that must have flourished for centuries on the spots where their remains are now entombed.

And even if the flora gave no certain evidence of the geniality of the climate that then pervaded the parallels of London and Paris, the associated fauna would of itself establish the belief. Gigantic sharks and rays (lamna, carcharodon, myliobatis), such as now frequent the Southern Ocean, crocodiles and turtles (crocodilus, chelonè, emys) in greater specific exuberance than is now known to the zoolo

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