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patella, cerithium, and the like, being the more common forms in the marine strata; while planorbis, paludina, and their congeners occur in the fresh-water limestones of the Weald thick as their modern species do on the marls of our lakes and marshes. The cephalopods now attain their meridian, and in variety of form, size, and numbers, stamp the period with one of its most peculiar aspects. Shellclad genera, like nautilus and ammonite, leave their chambered habitations in myriads; and naked genera, like the cuttle-fishes, are evidenced by thousands of those internal organisms (belemnites) which survive the decay of the softer structures. It is indeed the "reign of ammonites"-these beautiful shells occurring in hundreds of specific forms, in every stage of growth, and in the most diversified styles of external ornamentation. Along the exposed shore, in the land-locked bay, and out in the open waters of the old oolitic seas, these predaceous shell-clad cephalopods reign the lords of molluscan life, and mark the culmination of an order which now finds its only representative in the plainlooking nautilus of the Southern Ocean.

The fishes to which we next ascend belong exclusively to the great placoid and ganoid divisions-the soft-scaled orders (the ctenoids and cycloids) of the newer epoch being as yet unrepresented in oolitic waters. The placoids are chiefly rays and sharks, whose teeth (hybodus, acrodus, ganodus, &c.) and fin-spines (asteracanthus, nemacanthus, and myriacanthus) were the only preservable portions of their uncalcified skeletons. Many of these, like the cestracion of the Australian seas, were evidently fitted for the crushing of crustaceous and testaceous animals, others for the prehension of fishes, while some, more slenderly armed, gorged themselves, like their modern congeners, on the squids and cuttle-fishes that then thronged the ocean. The ganoids, now more ichthyic in their aspect, appear in nu

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merous generic forms (pachycormus, pycnodus, echmodus, lepidotus, &c.), the majority of which are peculiar to the mesozoic period, and many of them even restricted to the time of the lias and oolite. It is now, too, the high noon of reptilian development-" the Age of Reptiles"-when marine genera (ichthyosaurus and plesiosaurus) were the

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Ichthyosaurus; Long-necked Plesiosaurus; and Pterodactyle.

whale-like monarchs of the ocean; when crocodilians (teleosaurus and cetiosaurus) thronged the rivers and estuaries; turtles (chelone and platemys) traversed the muddy shores; gigantic land-saurians (megalosaurus, hylosaurus, and iguanodon) roamed, elephant-like, over the river-plains, or

browsed in the virgin forest; lizards (lacerta and macellodus) basked on the sunny cliffs; and bird-like genera (pterodacty

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Restored forms of Megalosaurus and Hylæosaurus-HAWKINS.

lus) winged the upper firmament. Every adaptation of form and function finds its exemplar in these ancient saurians, and the part now played by birds and mammals was then in a great measure discharged by reptiles. They were the representatives in time of the higher orders of vitalityoccupying every habitat, aquatic, terrestrial, and aerial, and fulfilling every function, herbivorous, carnivorous, and omnivorous. Everywhere they are the dominant forms, and though birds and mammals are coming more clearly on the stage, the great vital phase of creation was, for the time being, unmistakably reptilian.

This "Reign of Reptiles," as it is sometimes termed, has suggested to minds, more imaginative than logical, the idea of an epoch of incessant warfare and murder; and nothing is more common than pictorial delineations and high-wrought descriptions of reptilian carnage and cruelty.

Transferring the attributes of the infuriated human mind to the unreasoning brute, they picture every species lying in wait for his neighbour—writhing in savage combat for supremacy, and mangling with their horrid fangs even where prey does not become a necessity. Alas! for man's mistaken notion of creation's life-scheme; as if, even in a world of reptiles, there were not a thousand checks and compensations ever actively at work to secure the greatest happiness of the greatest numbers. No doubt the flesheater preyed on the plant-eater, and the weak succumbed where the strong exulted; but death comes unconsciously quick where the preyer strikes from necessity, and the fall of the sickly gives wider verge to the enjoyment of the healthy survivor. The wants of nature supplied, and then, as now, the gigantic herbivora rolled sportively among the over-topping herbage, or stood drowsily dreaming under the shade of the noonday forest; while the carnivora gambolled in the open waters, or lazily sunned themselves on the ebbing sea-shore. Wherever life prevails, there also is meted out to it its measure of enjoyment, and man only errs when, describing the lower animals, he invests them with passions and feelings unfortunately too frequently his own. But cold-blooded air-breathers, however varied in size, form, and function, were not destined to be the culminating orders in the world's life-scheme. The divine creational idea, fixed from the beginning, was steadily evolving itself into higher and higher types; and along with this overwhelming exuberance of reptiles, the line of triassic birds was continued in such forms as palæornis (ancient-bird), while in certain areas there appeared the higher manifestations of mammalian development. Small insectivorous quadrupeds-amphitherium (doubtful-beast), phascolotherium (pouched-beast), stereognathus (thick-jaw), plagiaulax (oblique-grooved tooth), &c.-have been detected

in the upper oolite, apparently marsupial in their structure, and pointing to the wombats, bandicoots, and phalangers of Australia as their nearest living analogues. From the number of these imbedded in a few square yards of a stratum near Swanage in Dorsetshire, we may confidently look forward to the discovery of many other mammalian forms— every condition of the period being favourable to the development of such a fauna.

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3

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Oolitic Mammals, natural size-1, Lower Jaw and Teeth of Phascolotherium;
2, Of Triconodon; 3, Of Plagiaulax.

Such are the phases of oolitic life, and such the conditions of sea and land, which its miscellaneous sediments seem to imply. Continuous lands of ample area for the growth of a varied flora, open free-flowing seas for an exuberant marine fauna, gigantic estuaries and river plains for the amphibious reptiles of the Weald, and over all a genial but periodically interrupted climate. We have as yet no means of determining the universal climatology of the period, but over the oolitic areas of the northern hemisphere the varying rings of coniferous growth would seem to indicate seasonal variations, while the prevailing aspect of the flora, the abundance of land reptiles, and the presence of small marsupials, point to conditions of general warmth and periodic drought, such as now obtain over the riverless plains of

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