The body of the iguanodon was then driven out to sea, and became imbedded in the sand of the ocean; in the like manner, as at the present day, bones of land quadrupeds may not only be engulphed in deltas, but also in the deposits of the adjacent sea.

The oolite is succeeded by the Wealden, green sand and chalk formations measuring 660 yards in thickness, and containing immense quantities of fresh water and marine remains, the species being almost all different from those in the older rocks, and none of them occurring in the newer. The Wealden is one of estuary origin, containing many fresh water shells, and the bones of enormous reptiles: one of which, the iguanodon, must have measured seventy feet from snout to tail, and been fourteen feet in girth round the body.* The chalk and green sand abound with marine remains. It appears certain that the beds of this wonderful formation add to the antiquity of the earth. Come when the solution may, there is little likelihood of it shortening, but every probability of it extending the period that has elapsed since God called into existence the "heavens and the earth."

The chalk is succeeded by the tertiary deposits, in which the existing species make their first appearance. In the lower or first of the tertiary formations, there are only about five per cent. of existing marine shells; in the second, or middle formation, the number of recent and extinct species is nearly equal; in the last, or newest of these deposits, the

* Let the reader visit the British Museum, and after examining the largest thigh-bone of the Iguanodon, repair to the Zoological Gallery, and inspect the recent Crocodilian reptiles, some twenty-five or thirty feet in length; and observe that the fossil bone equals, if not surpasses, in size the entire thigh of the largest of existing reptiles; then let him imagine this bone clothed with proportionate muscles and integuments, and reflect upon the enormous trunk which such limbs must have been destined to move and to sustain, and he will obtain a just notion of the appaling magnitude of the lizards which inhabited the country of the Iguanodon.

recent shells amount to ninety-five per cent.-circumstances which show a gradual increase of marine animal life, for a long series of ages previous to our historical epoch. The tertiary rocks in the neighborhood of Paris, and other places, abound with the remains of extinct quadrupeds allied to the tapirs with the bones of elephants, rhinoceroses, hippopotami, lions, tigers, and many other animals belonging to existing genera, but of different species from any now living. The teeth and bones of horses are often met with in the elephant bed, in Brighton cliffs; they are referable to a small species, about the size of a Shetland pony.*

"Yes! where the huntsman winds his natin horn,

And the couch'd hare beneath the covert trembles;
Where shepherds tend their flocks, and grows the corn;
Where Fashion on our gay Parade assembles-
Wild Horses, Deer, and Elephants have strayed,
Treading beneath their feet old Ocean's races."

Megatherium, (Fig 7.)-This leviathan of the vast plains

The bones of the Kangaroo have been also found in England. That the remains of an extinct species of gigantic Kangaroo should be found

of South America, which were once occupied by immense numbers of the race now entirely extinct, partakes of the generic character of the existing diminutive sloths. It rivalled in size the largest rhinoceros, was armed with claws of enormous length and power, its whole frame possessing an extreme degree of solidity. With a head and neck like those of the sloth, its legs and feet exhibit the character of the armadillo and the ant-eater. Some specimens of the animal give the measurement of five feet across the haunches, and the thigh bone was nearly three times as thick as that of the elephant. The spinal marrow must have been a foot in diameter, and the tail, at the part nearest the body, twice as large, or six feet in circumference. The girth of the body was fourteen feet and a half, and the length eighteen feet. The teeth were admirably adapted for cutting vegetable substances, and the general structure and strength of the frame for tearing up the ground in search of roots, wrenching off the branches of trees, and uprooting their trunks, on which it principally fed. "Heavily constructed, and ponderously accoutred," says Dr. Buckland, in his eloquent description of the megatherium, "it could neither run, nor leap, nor climb, nor burrow under the ground; and all its movements must have been necessarily slow. But what need of rapid locomotion to an animal whose occupation, of digging roots for food, was almost stationary? And what need of speed for flight from foes, to a creature whose giant carcase was encased in an impenetrable cuirass, and who, by a single pat of his paw, or lash of his tail, could in an instant have demolished the couguar or the

in the fissures of the rocks, and in the caverns of Australia, a country in which marsupial animals are the principal existing mammalia, is a fact that will not excite much surprise; but that beings of this remarkable type of organization should ever have inhabited the countries situated in the latitude of the European continent and of Great Britain, would never have been suspected, but for the researches of the geologist.

crocodile? Secure within the panoply of his strong armour, where was the enemy that would dare encounter this leviathan of the Pampas? or in what more powerful creature can we find the cause that has effected the extirpation of his race? His entire frame was an apparatus of colossal mechanism, adapted exactly to the work it had to do. Strong and ponderous in proportion as this work was heavy and calculated to be the vehicle of life and enjoyment to a gigantic race of quadrupeds, which, though they have ceased to be counted among the living inhabitants of our planet, have in their fossil bones left behind them imperishable monuments of the consummate skill with which they were constructed."

The oolite quarries of Portland have been long remarkable for their containing certain strata called the "dirtbeds," in which the stems and branches of coniferous trees and cycadeæ* are found in considerable abundance. Many of the trees as well as the plants are still erect (see Fig 8.), with their roots ramified in the dirt-beds, which appears to be the soil in which they grew. "On my visit," says Dr. Mantell, "to the island in the summer of 1832, the surface of a large area of the dirt-bed was cleared, preparatory to its removal, and a most striking phenomenon was presented to my view. The floor of the quarry was literally strewed with fossil wood, and I saw before me a petrified tropical forest; the trees and plants like the inhabitants of the Alg, in the Arabian story, being converted into stone, yet still maintaining their place, which they occupied when alive! Some of the trunks were surrounded by a conical mound of calcareous matter, which had evidently once been earth, and had accumulated around the base and roots of the trees. The stems were generally three or four feet high, their summits being jagged and splintered, as if they had been

* A genus of plants allied to the palms and ferns.

-an appearance which

corn and wrenched off by a hurricanemany trees in this neighborhood (Bristol) after the late storm, strikingly resembled. Some of the trunks were two feet in diameter, and the united fragments of one tree measured upwards of thirty feet in length; in other specimens, branches were attached to the stem. In the dirt-bed there were many trunks lying prostrate, and fragments of branches. The fossil plants are called Cycadeodia, by Dr. Buckland, from their analogy to the recent Cycas and Zamia, but for which M. Adolphe Brongniart has established a new genus, named Mantellia. The plants occurred at intervals between the trees, and the dirt-bed was so little consolidated, that I dug up with a spade, as from a floor, seveeral specimens that must have been on the very spot on which they grew, like the columns of Puzzioli, preserved erect amidst all the revolutions which the surface of the earth have subsequently undergone, and beneath the accumulated spoils of numberless ages. The trees and plants are completely petrified by silex or flint."

From what has been stated, it is evident, that after the marine strata, forming the base of the isle of Portland, were deposited at the bottom of a deep sea, and had become consolidated, the bed of that ancient ocean was elevated above the level of the waters, became dry land, and was covered by forests. How long this new country existed cannot now be ascertained; but that it flourished for a considerable period is certain, from the number and magnitude of the trees of the petrified forest. In the isle of Purbeck, traces of the dirt-bed, with trunks of trees, are seen be neath the fresh water limestone of the Weald; a proof that, before the deposition of the Purbeck marble could have taken place, the petrified forest must have sunk to the depth of many hundred feet.

Space will not permit us to describe the other varieties of the vegetable kingdom which occur in secondary strata;