are amalgamated at their extremities; the heel-bone (calcaneum) is nearly half a yard in length; the haunch-bones (ilia) are from four to five feet across at their crests; and the bodies of the vertebrae at the root of the tail are from five to seven inches in diameter, from which it has been computed that the circumference of the tail at this part might have been from five to six feet.  The length of the fore-foot is about a yard, and the toes are armed with powerful curved claws.  It is known now that the Megathere, in spite of its enormous weight and ponderous construction, walked, like the existing Ant-eaters and Sloths, upon the outside edge of the fore-feet, with the claws more or less bent inwards towards the palm of the hand.  As in the great majority of the Edentate order, incisor and canine teeth are entirely wanting, the front of the jaws being toothless.  The jaws, however, are furnished with five upper and four lower molar teeth on each side.  These grinding teeth are from seven to eight inches in length, in the form of four-sided prisms, the crowns of which are provided with well-marked transverse ridges; and they continue to grow during the whole life of the animal.  There are indications that the snout was prolonged, and more or less flexible; and the tongue was probably prehensile.  From the characters of the molar teeth it is certain that the Megathere was purely herbivorous in its habits; and from the enormous size and weight of the body, it is equally certain that it could not have imitated its modern allies, the Sloths, in the feat of climbing, back downwards, amongst the trees.  It is clear, therefore, that the Megathere sought its sustenance upon the ground; and it was originally supposed to have lived upon roots.  By a masterly piece of deductive reasoning, however, Professor Owen showed that this great “Ground-Sloth” must have truly lived upon the foliage of trees, like the existing Sloths—­but with this difference, that instead of climbing amongst the branches, it actually uprooted the tree bodily.  In this tour de force, the animal sat upon its huge haunches and mighty tail, as on a tripod, and then grasping the trunk with its powerful arms, either wrenched it up by the roots or broke it short off above the ground.  Marvellous as this may seem, it can be shown that every detail in the skeleton of the Megathere accords with the supposition that it obtained its food in this way.  Similar habits were followed by the allied Mylodon (fig. 261), another of the great “Ground-Sloths,” which inhabited South America during the Post-Pliocene period.  In most respects, the Mylodon is very like the Megathere; but the crowns of the molar teeth are flat instead of being ridged.  The nearly-related genus Megalonyx, unlike the Megathere, but like the Mylodon, extended its range northwards as far as the United States.

[Illustration:  Fig. 260.—­Megatherium Cuvieri.  Post-Pliocene, South America.]