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tion of the tusks, such as are found in no other living or fossil animal.

The form of the molar teeth, Pl. 2. C. Fig. 3, approaches, as we have stated, most nearly to that of the molar teeth in Tapirs; but a remarkable deviation from the character of Tapirs, as well as of every other quadruped, consists in the presence of two enormous tusks, placed at the anterior extremity of the lower jaw, and curved downwards, like the tusks in the upper jaw of the Walrus. (Pl. 2. C. 1. 2.)

I shall confine my present remarks to this peculiarity in the position of the tusks, and endeavour to show how far these organs illustrate the habits of the extinct animals in which they are found. It is mechanically impossible that a lower jaw, nearly four feet long, loaded with such heavy tusks at its extremity, could have been otherwise than cumbrous and inconvenient to a quadruped living on dry land. No such disadvantage would have attended this structure in a large animal destined to live in water; and the aquatic habits of the family of Tapirs, to which the Dinotherium was most nearly allied, render it probable that, like them, it was an inhabitant of fresh-water lakes and rivers. To an animal of such habits, the weight of the tusks sustained in water would have been no source of inconvenience; and, if we suppose them to have been employed, as instruments for raking and grubbing up by the roots large aquatic vegetables from the bottom, they would, under such service, combine the mechanical powers of the pick-axe with those of the horse-harrow of modern husbandry. The weight of the head, placed above these downward tusks, would add to their efficiency for the service here supposed, as the power of the harrow is increased by being loaded.

The tusks of the Dinotherium may also have been applied with mechanical advantage to hook the head of the animal to the bank, with the nostrils sustained above the water, so as to breathe securely during sleep, whilst the body remained floating, at perfect ease, beneath the surface: the animal

might thus repose, moored to the margin of a lake or river, without the slightest muscular exertion, the weight of the head and body tending to fix and keep the tusks fast anchored in the substance of the bank; as the weight of the body of a sleeping bird keeps the claws clasped firmly around its perch. These tusks might have been farther used, like those in the upper jaw of the Walrus, to assist in dragging the body out of the water; and also as formidable instruments of defence.

The structure of the scapula, already noticed, seems to show that the fore leg was adapted to co-operate with the tusks and teeth, in digging and separating large vegetables from the bottom. The great length attributed to the body, would have been no way inconvenient to an animal living in the water, but attended with much mechanical disadvantage to so weighty a quadruped upon land. In all these characters of a gigantic, herbivorous, aquatic quadruped, we recognise adaptations to the lacustrine condition of the earth, during that portion of the tertiary periods, to which the existence of these seemingly anomalous creatures appears to have been limited.

SECTION II.

MEGATHERIU M.

As it will be quite impossible, in the present Treatise, to give particular descriptions of the structure, even of a few of the fossil Mammalia, which have been, as it were, restored again to life by the genius and industry of Cuvier; I shall endeavour to illustrate, by the details of a single species, the method of analytical investigation, that has been applied by that great philosopher to the anatomy both of fossil and recent animals.

The result of his researches, as recorded in the Ossemens Fossiles, has been to show that all fossil quadrupeds, however differing in generic or specific details, are uniformly constructed on the same general plan, and systematic basis of organization as living species; and that throughout the various adaptations of a common type to peculiar functions, under different conditions of the earth, there prevails such universal conformity of design, that we cannot rise from the perusal of these inestimable volumes, without a strong conviction of the agency of one vast and mighty Intelligence, ever directing the entire fabric, both of past and present systems of creation.

Nothing can exceed the accuracy of the severe and logical demonstrations, that fill these volumes with proofs of wise design, in the constant relation of the parts of animals. to one another, and to the general functions of the whole body. Nothing can surpass the perfection of his reasoning, in pointing out the beautiful contrivances, which are provided in almost endless variety, to fit every living creature to its own peculiar state and mode of life. His illustration of the curious conditions, and concurrent compensations that are found in the living Elephants, apply equally to the extinct fossil species of the same genus; and similar exemplifications may be extended from the living to the extinct species of other genera, e. g. Rhinoceros, Hippopotamus, Horse, Ox, Deer, Tiger, Hyæna, Wolf, &c., that are usually associated with the Elephant in the fossil state.

The animal I shall select for my present purpose is that most extraordinary fossil creature, the Megatherium, (see Pl. 5,) an animal, in some parts of its organization, nearly allied to the Sloth, and, like the Sloth, presenting an apparent monstrosity of external form, accompanied by many strange peculiarities of internal structure, which have hitherto been but little understood.

The Sloths have afforded a remarkable exception to the conclusions which naturalists have usually drawn, from their

study of the organic structure and mechanism of other animals. The adaptation of each part of the body of the Elephant, to produce extraordinary strength, and of every member of the Deer and Antelope to give agility and speed are too obvious to have escaped the attention of any scientific observer; but, it has been the constant practice of naturalists, to follow Buffon in misrepresenting the Sloths, as the most imperfectly constructed among all the members of the animal kingdom, as creatures incapable of enjoyment, and formed only for misery.

The Sloth does, indeed, afford the greatest deviations from the ordinary structure of the living quadrupeds; and these have been erroneously considered as imperfections in its organization, without any compensating advantage. I have elsewhere* attempted to show that these anomalous conditions are so far from being defects, or sources of inconvenience in the Sloth, that they afford striking illustrations of the varied contrivances, whereby the structure of every creature is harmoniously adapted to the state in which it was destined to live. The peculiarities of the Sloth, that render its movements so awkward on the earth, are fitted with much advantage to its destined office of living entirely upon trees, and feeding upon their leaves: so also, if we consider the Megatherium with a view to its province of digging and feeding upon roots, we shall, in this habit, discover the explanation of its unusual structure, and apparently incongruous proportions; and find, in every organ, a relation of obvious convenience, and of adaptation to the office it had to discharge.†

* Linnean Transactions, Vol. XVII. Part 1.

The remains of the Megatherium have been found chiefly in the southern regions of America, and most abundantly in Paraguay; it appears also to have extended on the north of the equator as far as the United States. We have for some time, possessed detailed descriptions of this animal by Cuvier, Oss. Foss. vol. 5, and a series of large engrav ings, by Paxder and D'Alton, taken from a nearly perfect skeleton, sent

It will be my present object to enter into such a minute investigation of some of the more remarkable parts of this animal, viewing them with a constant reference to a peculiar mode of life, as may lead to the recognition of a system of well connected contrivances, in the mechanism of a creature apparently the most monstrous, and seeming to present the most ill-assorted proportions, that occur throughout the entire range of the animal kingdom.

We have here before us a gigantic quadruped, (see Pl. 5, Fig. 1,) which at first sight appears not only ill-proportioned as a whole, but whose members also seem incongruous, and clumsy, if considered with a view to the functions and corresponding limbs of ordinary quadrupeds: let us only examine them with the aid of that clue, which is our best and essential guide in every investigation of the mechanism of the animal frame; let us first infer from the total composition and capabilities of the machinery, what was the general nature of the work it was destined to perform; and from the character of the most important parts, namely, the feet and teeth, make ourselves acquainted with the food these organs were adapted to procure and masticate; and we shall find every other member of the body acting in harmonious subordination to this chief purpose in the animal economy.

In the case of ordinary animals, the passage from one

in 1789 from Buenos Ayres to Madrid. Dr. Mitchell and Mr. Cooper have described, in the Annals of the Lyceum of Natural History of New York, May, 1824, some teeth and bones found in the marshes of the Isle of Skiddaway, on the coast of Georgia, which correspond with the skele ton at Madrid. Cuvier, Vol. V. part 2, p, 519.-In the year 1832, many parts of another skeleton were brought to England by Woodbine Parish, Esq., from the bed of the river Salado, near Buenos Ayres: these are placed in the museum of the Royal College of Surgeons in London, and will be described in the Trans. Geol. Soc. Lond. Vol. III., N. S., Part 3, by my friend Mr. Clift, a gentleman from whose great anatomical knowledge, I have derived most important aid, in my investigation of this animal.

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