anodon are partly composed of bone, gradually becoming softer from the edge inwards, and partly of enamel, by which they are surrounded; the result of this contrivance being the formation of a slant surface of the crown of the tooth, and therefore of a sharp cutting edge. While young, the tooth presents a sharp edge, and is lancet-shaped as it grows further out from the jaw, and is then a powerful instrument, well adapted to separate tough vegetable fibres; while in its most advanced state it ceases to be adapted to this purpose, but is strong and flat, and at the same time uneven, the pulp of the tooth projecting from the surface, which is worn so as to be nearly horizontal, and forming a transverse ridge. The teeth therefore begin by being incisors, and in the course of time, as they become worn, they pass into the condition of grinders-a curious change, providing for the animal a perpetual supply of teeth of all kinds, some enabling it to nip off tough vegetable food, and others helping to grind that food properly before it is committed to the stomach.

A Bony Structure of Great Strength.

The vertebral column of the iguanodon is on a scale commensurate with the vast bulk of the animal. The vertebræ themselves have nearly flat surfaces, and are large and somewhat wedge-shaped like those of the crocodile. The neck is not known, since no vertebræ have yet been found belonging to this part. The sarcum, or that part of the back-bone, cemented together to distribute the weight of the body on the hinder extremities, includes five vertebræ, as in the megalosaurus; and in one specimen this continuous solid ridge of bone measures seventeen inches in length, and its breadth, though only eight inches at the fore part, becomes as much as thirteen inches towards the hinder part. The magnitude, both in diameter and length, of the thigh and leg bones, corresponds well with the large portion of the spine thus grasped, as it were, by the bones of the pelvis, and strongly points to the terrestrial habits of the animal. The total length of the extremities seems, in some cases, to have exceeded eight or even nine feet, and the bones of the foot are gigantic even beyond the proportions thus indicated, since one of the separate bones measures thirty inches in length, and the last joint of the toe, to which a claw was attached, is five inches and a half long. There was thus an ample base for the vast column supporting the body.

The tail of the iguanodon was probably very much shorter in proportion than that of crocodiles, and was very dissimilar. It must, notwithstanding, have been large, and flattened laterally, being of considerable breadth in the vertical direction near its attachment to the body. The ribs were very large, broad, and long.

While the bones or the extremities were perhaps six or eight times larger than those of the most gigantic alligator, the whole length of the iguanodon is not likely to have exceeded thirty feet. Even then, however, allowing about three feet for the head, and assuming that the neck was short, and that the tail was about thirteen feet long, which it is calculated would be the extreme size, we still have a length of twelve feet for the body, and this is much more than is seen in the trunk of any living animal. The body being of this length, and perhaps of more than corresponding bulk, and lifted many feet from the ground, reaching perhaps to the height of twelve or fifteen feet, must have indeed been sufficiently monstrous, and departed widely enough from any known animal to justify

the accounts that have been given of its strange and marvelous proportions.

It is difficult to confine the imagination within due bounds when we endeavor to recall scenes enacted during the earlier periods of the earth's history, and to picture these past events without running into extravagance, and without overstepping the limits of simplicity and probability, which should always characterize natural history. There is, however, no need of exaggeration in depicting the wonders of those ancient periods. Let us imagine ourselves placed on a projecting headland or hill of

mountain limestone, anciently, as now forming a prominent and picturesque object, but commanding a view of the open sea, which then covered the greater part of our island. Placed in imagination in this commanding position, let us endeavor to recall the scenes once enacted near some tract of low flat land-a sandy shore of the oolitic period-on which, at a distance, a few solitary palm trees stand out against the blue sky, but which is backed by a more luxuriant growth of pines and ferns, extending towards the interior, and crowning the tops of distant high ground.

The first object that attracts attention might be one of the crocodilian animals with its long slender snout, and with extremities admirably adapted for swimming, combining those peculiarities of structure which distinguish the teleosaurus. This animal might be seen moving slowly, and not without difficulty, towards the water, but when there, darting abruptly along, pursuing and devouring the small fishes that swarmed about the shallows; these fishes, sluggish in their nature, and chiefly feeding on the molluscs which live near the shore, falling a ready and abundant prey. Many other crocodilian monsters, of similar habits, but more or less adapted for a marine life, might also have been seen wandering about. Leviathans of the Antediluvian Seas.

While, however, this was going on in the near vicinity of land, our supposed position would enable us to watch also the open sea at a little distance. Here we could not fail being struck with that gigantic reptile, the cetiosaurus, easily recognized by the dark outline of its huge head raised partly above the surface to enable the animal to breathe, while at the distance of some twenty yards from this would be seen its great fishlike tail. Could our power of vision enable us to see beneath the surface, there might also be observed those singular webbed feet, and enormous toes armed with long powerful claws, which so strikingly characterize this creature.

But another of the monsters of the deep demands our notice—a truly marine reptile-gigantic in its proportions, admirably adapted for rapid motion, and combining some of the terrestrial and crocodilian peculiarities of the long-necked plesiosaurus, with the compact proportions of the great fish-lizard. Its huge crocodilian head contrasts strongly with the porpoise-like body, which is attached without any intervening neck; and its powerful elongated extremities make up for the absence of a vertical tail-fin. The sharks, which were still abundant and powerful, and even the ichthyosaurus itself, could scarcely have escaped from these terrible

enemies.

Having thus obtained glimpses of the sea and its inhabitants, let us

next turn our attention to the adjacent land. The long-snouted and other crocodiles, which have gorged themselves with fish in the shallow water, now sleep half buried in the muddy and naked plains on shore. Some of them, eighteen or twenty feet long, advance on land with difficulty, their extremities being far better adapted to swimming than walking. Presently a noise is heard, and a huge animal advances, whose true nature and habits we are at first at a loss to understand. In its general proportions it is far longer and also taller than the largest elephant; its body hangs down near the ground, but its legs are like the trunks of great forest trees, and its feet form an ample base for the vast columns which press upon them. Instead of long tusks, large grinding teeth, and a trunk like that of the elephant, this animal has an exceedingly elongated and narrow snout, armed throughout with ranges of sharp and strong knife-like teeth. The monster approaches, and trodden down with one of its feet, armed with powerful claws, or caught between its long and narrow jaws, our crocodile is devoured in an instant.

Insects of Marvelous Brilliancy.

But there is yet another scene for us to contemplate. Still remaining at no great distance from the shore, but advancing inland towards the forest, let us watch the golden beetles, and the beautiful dragon-flies and other insects as they flit past in all the brilliancy and cheerfulness of luxuriant and untamed nature. The lofty forest trees, perhaps not much unlike some existing but southern pines, are woven together with thick underwood; and the open country, where it is not wooded, is brown with numerous ferns, still the preponderating vegetation, and distributed in extensive groups. Here and there a tree is seen, overturned and lying at its length upon the ground, preserving its shape, although thoroughly rotten, and serving as the retreat of the scorpion, the centipede and many beetles. A few quadrupeds, not larger than rats, are distinguished at intervals, timid even in the absence of danger, and scarcely appearing from their shelter without great precaution.

A strangely formed animal, however, is perceived running along upon the ground: its general appearance in motion is that of a bird, but its body and long neck, its head and wings, are not covered with feathers, but are either quite bare, or perhaps resplendent with glittering scales; its proportions are quite unlike those of any known animal; its head is enormously long, and like that of a crocodile; its neck long and outstretched, or thrown back on the body; its fore extremities have four free toes, but the fifth toe folded down on the body; its hind legs are short, and its feet perhaps webbed. This animal, running along upon the