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It remains to consider, of what use this cuirass could have been to the gigantic animal on which it probably was placed. As the locomotive organs of the Megatherium indicate very slow power of progression, the weight of a cuirass would have afforded little impediment to such tardy movements; its use-was probably defensive, not only against the tusks and claws of beasts of prey, but also, against the myriads of insects, that usually swarm in such climates as those wherein its bones are found; and to which an animal that obtained its food by digging beneath a broiling sun, would be in a peculiar degree exposed. We may also conjecture it to have had a farther use in the protection afforded by it to the back, and upper parts of the body; not only against the sun and rain, but against the accumulations of sand and dust, that might otherwise have produced irritation and disease.*

Mr. Parish. Although no armour was found with the fragments of the large skeleton, in the bed of the Salado, the rough broad flattened surface of a part of the crest of the ileum of this skeleton, (see PI. 5, Fig. 2. r, s,) and the broad condition of the summit of the spinous processes of many vertebra:, and also of the superior convex portion of certain ribs on which the armour would rest, afford evidence of pressure, similar to that we find on the analogous parts of the skeleton of the Armadillo, from which we might have inierred that the Megatherium also was covered with heavy armour, even had no such armour been discovered near bones of this animal in other parts of the same level district of Paraguay. In all these flattened bones the effects of pressure are confined to those parts of the skeleton, on which the armour would rest, and are such as occur in a remarkable degree in the Armadillo.

* To animals that dig only occasionally, like Badgers, Foxes, and Rabbits, to form a habitation beneath the ground, but seek their food upon the surface, a defence of this kind would not only have been unnecessary but inconvenient.

The Armadillo and Chlamyphorus are the only known animals that have a coat of armour composed of thick plates of bone, like that of the Megatherium. As this peculiar covering is confined to these quadrupeds, we can hardly imagine its use to be solely for protection against other beasts and insects; but as the Armadillo obtains its food by digging in. the same dry and sandy plains, which were once inhabited by the Megatherium, and the Chlamyphorus lives almost entirely in burrows beneath the surface of the same sandy regions; they both probably receive from their cuirass the same protection to the upper parts of their bodies from sand and dust, which we suppose to have been afforded by its cuirass to the Megatherium. The Pangolins are covered with a different kind of armour, composed of horny moveable scales, in which there is no bony matter.

Conclusion.

We have now examined in detail the skeleton of an extinct quadruped of enormous magnitude; every bone of which presents peculiarities, that at first sight appear imperfectly contrived, but which become intelligible when viewed in their relations to one another, and to the functions of the animal in which they occur.

The size of the Megatherium exceeds that of the existing Edentata, to which it is most nearly allied, in a greater degree than any other fossil animal exceeds its nearest living congeners. With the head and shoulders of a Sloth, it combined in its legs and feet, an admixture of the characters of the Ant-eater, the Armadillo, and the Chlamyphorus; it probably also still farther resembled the Armadillo and Chlamyphorus, in being cased with a bony coat of armour. Its haunches were more than five feet wide, and its body twelve feet long and eight feet high; its feet were a yard in length, and terminated by most gigantic claws; its tail was probably clad in armour, and much larger than the tail of any other beast, among extinct or living terrestrial Mammalia. Thus heavily constructed, and ponderously accoutred, it could neither run, nor leap, nor climb, nor burrow under the ground, and in 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 carcass was encased in an inpenetrable 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 Crocodile? Secure within the panoply of his bony 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?lure and functions of these extinct families of reptiles; and not only enables us to infer from the restoration of their skeletons, what may have been the external form of their bodies; but instructs us also as to their economy and habits, the nature of their food, and even of their organs of digestion. It farther shows their relation to the then existing condition of the world, and to the other forms of organic life with which they were associated.

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. Each limb, and fragment of a limb, forming co-ordinate parts of a well-adjusted and perfect whole; and through all their deviations from the form and proportion of the limbs of other quadrupeds, affording fresh proofs of the infinitely varied, and inexhaustible contrivances of Creative Wisdom.

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The remains of these reptiles bear a much greater resemblance to one another, than to those of any animals we discover in deposites preceding or succeeding the secondary series.*

The species of fossil Saurians are so numerous, that we can only select a few of the most remarkable among them, for the purpose of exemplifying the prevailing conditions of animal life, at the periods when the dominant class of animated beings were reptiles; attaining, in many cases, a magnitude unknown among the living orders of that class, and which seems to have been peculiar to those middle ages of geological chronology, that were intermediate between the transition and tertiary formations.

During these ages of reptiles, neither the carnivorous nor lacustrine Mammalia of the tertiary periods had begun to appear; but the most formidable occupants, both of land and water, were Crocodiles, and Lizards; of various forms, and often of gigantic stature, fitted to endure the turbulence, and continual convulsions of the unquiet surface of our infant world.

When we see that so large and important a range has been assigned to reptiles among the former population of

• The oldest strata in which any reptiles have yet been found are those connected with the magnesian-limestone formation. (PI. 1, Sec. 16.) The existence of reptiles allied to the Monitor in the cupriferous slate and zechstein of Germany, has long been known. In 1834, two species of reptiles, allied to the Iguana and Monitor, were discovered in the dolomitic conglomerate, on Durdham Down, near Bristol

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our planet, we cannot but regard with feelings of new and unusual interest, the comparatively diminutive existing orders of that most ancient family of quadrupeds, with the very name of which we usually associate a sentiment of disgust. We shall view them with less contempt, when we learn from the records of geological history, that there was a time when reptiles not only constituted the chief tenants and most powerful possessors of the earth, but extended their dominion also over the waters of the seas; and that the annals of their history may be traced back through thousands of years, antecedent to that latest point in the progressive stages of animal creation, when the first parents of the human race were called into existence.

Persons to whom this subject may now be presented for the first time, will receive, with much surprise, perhaps, almost with incredulity, such statements as are here advanced. It must be admitted, that they at first seem much more like the dreams of fiction and romance, than the sober results of calm and deliberate investigation; but to those who will examine the evidence of facts upon which our conclusions rest, there can remain no more reasonable doubt of the former existence of these strange and curious creatures, in the times and places we assign to them; than is felt by the antiquary, who, finding the catacombs of Egypt stored with the mummies of Men, and Apes, and Crocodiles, concludes them to be the remains of mammalia and reptiles, that have formed part of an ancient population on the banks of the Nile.

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