Page:The Zoologist, 1st series, vol 1 (1843).djvu/312

284 "the inverted position of the soles of his hind feet." Dr. Lund, however, saw enough in the living sloth to lead him to very decided conclusions respecting the extinct Megalonyx; differing however, as they do, from those of Professor Owen, we presume not to speak of them as conclusive.

"Now, the Megalonyx, like the sloth, is provided with powerful clavicles; like it, also, its anterior extremities are longer than the hind; its toes are armed with immense claws; and lastly, the sole of its hind foot is turned inwards instead of downwards.

"The first of these characters, or the existence of perfect clavicles, proves that this animal used its fore extremities for more purposes than for walking; which position I take to be incontrovertible, as it is founded on a rule that has no exception among mammals. The purposes for which mammals, provided with clavicles, employ their anterior extremities, are the following:—1st, for flying, as in the bats, with which we have here nothing to do; 2dly, for the apprehension of food, and the bringing it to the mouth, either with one hand, as in the apes, or with two, like most rodents, some marsupials, &c. Now, the first of these purposes requires a peculiar disposition of the fingers, and a certain freedom of motion in them; which conditions are both wanting in the Megalonyx, notwithstanding this animal, as well as the Megatherium, has in reality been classed by Wagler among apes. The second purpose is confined to animals that have short fore-limbs, and whose dental system is adapted to gnaw substances which they hold in their paws; which conditions being also inapplicable to the Megalonyx, there can be no occasion to dwell longer on them. Thirdly, for tearing asunder their prey, as in the feline tribes. This purpose requires only an imperfect development of the clavicles, but at the same time, a peculiar arrangement in the shape and attachment of the claws; which, again, is not the case in the Megalonyx. Besides, the dental system proves it to have been graminivorous; although authors have not been wanting (as Jefferson and Faujas) who have placed it among the Carnivora.

"There remain, therefore, only two functions that are exercised by animals provided with bones for the attachment of claws; viz., digging and climbing. And it is the more necessary to confine our attention to these two points, inasmuch as we see that all animals belonging to the same order as Megalonyx, exercise one or the other of these functions. Their immediate instruments for these purposes are claws, which consequently are powerfully developed in all; but in none in so high degree as in the extinct genera Megalonyx and Megatherium: in these they have reached the highest degree of development we yet know in the animal kingdom. It would be contrary to all experience in Natural History, to suppose that an organ should lose its function and significance precisely at the point where it is most perfectly developed. We cannot doubt, therefore, that the powerful claws with which we find Megalonyx and Megatherium armed, have had their use. We may even conclude with certainty, that the habits of the animals were closely connected with these organs, and that their very existence depended on them. Now, as we only know of two uses for strong claws in mammals, digging and climbing; and as these two purposes require different anatomical arrangements; it will not be very difficult to decide for which of them the powerful organs in the extraordinary creatures we are considering were intended. We find among the animals the most perfectly organized with respect to burrowing, such as the mole &c, that the claws are strong, long, broad, and nearly of equal size, that all the digits arc provided with similar claws, and are extended in almost the same plane