the oolite, but with new and peculiar genera of the same great divisions; while for the first time the ctenoids and cycloids, which are now the prevailing orders of ichthyic life, make their first appearance. Among the placoids, as indicating their fossil teeth, ptychodus, hybodus, acrodus, and lamna are the dominant genera; among the ganoids, gyrodus, pycnodus, and macropoma; while the cycloids show osmeroides, hypsodus, saurocephalus, and the like; and the ctenoids, the perch-like forms of beryx and berycopsis.

1, Beryx Lewesiensis; 2, Osineroides Mantelli-MANTELL.

When we turn to the reptiles, a few species of plesiosaurus and ichthyosaurus still linger in the ocean; a solitary iguanodon represents the gigantic land-tribes; and pterodactyles, in lessening flocks, wing the sea-cliffs or skim the surface of the creeks and river-mouths. The crocodiles,

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lizards, and turtles are represented by several genera; but on the whole the meridian of reptilian life is past, and the huge and varied forms of the oolite are now extinct, or rapidly disappearing. Of birds and mammals the highly marine beds of the chalk have yielded little more than the merest indications (cimoliornis, bird-of-the-chalk-marl, &c.), but as these seem to point to the higher types of the rapacious birds and true mammals, we may rest assured of the existence of intervening orders, and look forward with hope to the discovery of their remains.

With the Chalk, which closes the long and prolific line of mesozoic life, we lose sight of many tribes, and families, and genera, but not, as is sometimes sweepingly asserted, of every species that up to that time had given character to the onward phases of vitality. The passage from the mesozoic to the cainozoic was as gradual as that from the paleozoic to the mesozoic, and if a break shall appear to exist in some districts, we cannot accept this as more than a mere local and limited phenomenon. The submergence of old lands, and the elevation of the sea-bed into new islands and continents, is a slow and gradual process; it is never cataclysmal save over the most partial and isolated tracts; and only in such tracts is there a chance of any genus or species being suddenly extinguished. As the gift of life is handed from generation to generation within certain limits of variety, so epoch passes it on to epoch within the wider limit of specific change, but this so imperceptibly that it is only after the lapse of ages the difference becomes apparent. Viewed at these wide intervals, the paleozoic flora seems essentially exogenous; endogens and gymnogens prevail in the mesozoic; and now the cainozoic is about to be characterised by the newer and higher manifestations of the exogens. In like manner

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with the fauna: we rise (speaking in general terms) from a world of cold-blooded air-breathers in the palæozoic to cold-blooded air-breathers in the mesozoic, and from these again to the warm-blooded air-breathers of the cainozoic era. If fishes were the dominant vertebrates in palæozoic times, reptiles were undoubtedly so during the mesozoic; and now, in the cainozoic, the mammals (so feebly represented in the past) are about to assume the chief importance. The great march of life is not only ever forward, but ever upward. It is not merely that creation is concomitant with extinction, but the new creations are ever assuming more exalted ordinal forms of the same primal patterns.

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