BRADYPUS, a genus of Mammals belonging to the order Edentate of Cuvier, and together with the genus Oulu, or Chobrpus, composing a small family to which Cuvier gave the appellation of Tardigrada, from the peculiar conformation of their extremities, and the remark able slowness of their pace. Both these genera were formerly included by Linnaeus in the same group, under the common name of Bradypus, To enable us clearly to comprehend the nature and functions of these animals, it will be necessary to cuter into a short description of parts of their osteological structure. The view here given of the skeleton of the Sloth (Brodypus tridactylus) seems to indicate n distortion of certain parts and proportions altogether opposed to freedom of motion, nt least of that kind of motion with which wo are familiar in ordinary quadrupeds. The arm and fore-arm taken together are nearly twice as long as the leg and thigh, so that if the animal attempts to walk on all-fours it is obliged to trail itself painfully and slowly on its elbows, and if it stands upright on the hind legs the arms are so long that the fore fingers touch the ground. This disproportion between the anterior and posterior extremities, ftiounly deprives these animals of the power of moving on a plain murtiee with that speed which is so admirable in the generality of quadrupeds; and accordingly we are assured by all observers, that their mode of progression under these circumstances is of the most slow and painful nature. The Sloths however are not terrestrial animals, bualive entirely among the thick branches of trees in the moat extensive and solitary forests. This remarkable disproportion of their fore-arms is common to another genus of arboreal manmade, the real apes, in which, far from retarding their motions, this peculiar etructuro is of the most essential import ance in adding to their agility. But the Sloths partake of none of the accessory advantages which the Apes poaseas. They have no opponeable thumb ; their fingers are short, and eo perfectly rigid that the joints ossify at a very early period of the animal's life, leaving them totally incapable of individual motion, whilst they are at the same time so completely enveloped in the common integuments of the hand that nothing is to be seen externally except the immense crooked claws with which they are provided. The wrist and ankle also are articulated or joined to the fore-arm and leg in an oblique direction ; so that the palm or sole, instead of being directed down wards towards the surface of the ground, as in other animals, is turned inwards towards the body, in such a manner as to render it impossible for the Sloth to place the sole of its foot straight down upon a level surface, but to compel it, under such circumstances, to rest upon the external edge of the foot. This position is obviously
but ill adapted for ease or facility of motion. But there is still If placed upon a plain surface, the Sloth moves with difficulty and only by seizing upon the little asperities which he finds in his way, and by that means dragging his body slowly forwards, just as we may observe a bat to do under similar circumstances. But this is a situa tion equally foreign to the habits and economy both of the Sloth and of the bat ; and we are no more justified in judging of the nature of the one under these circumstances, than we should be in reasoning upon the habits of the other. The Sloth is eminently an arboreal quadruped : it is produced, it lives, and it dies in the trees ; it very another singularity in the structure of the foot of this animal which materially increases its difficulties of progression on a plain surface. This arises from the peculiar form of the last phalanx or joint of the fingers and toes, that, namely, which gives insertion to the claws, and which is articulated with the second phalanx in such a manner as to permit the fingers and claws to be strongly bent inwards along the palm and arm, but at the same time prevents the animal from raising them upwards or opening the hand beyond a certain position. This structure is exactly the reverse of what we observe in the com mon cat, which has the phalanxes of the toes formed in such a manner as to keep the claws habitually retracted or drawn up, so that it requires a considerable degree of muscular force to extend or depress them. In the Sloths, on the contrary, they are naturally depressed in the position represented in the figure of the skeleton, and the muscular force is exerted to expand or open them. The claws themselves are of a size altogether enormous, surpassing the entire foot in length. They are so sharp and crooked that they readily seize upon the smallest inequalities in the bark of the trees and branches among which the animals habitually reside ; and, united to the great muscular strength and rigid formation of the extremities, furnish the most powerful weapons of defence. Nor are the form and articulation of the posterior extremities less singular than those of the anterior. The formation of the pelvis alone is of such a nature as to render it im possible for the Sloths to walk after the manner of ordi nary quadrupeds ; and 'the mode in which the hind legs are articulated with the pelvis, to use the expression of Baron Cuvier, seems almost ex pressly arranged for the purpose of de priving the animal of the use of its legs altogether.