_Lestodon_ is another allied genus, which seems to possess canines. At any rate, in front of the four molars, and separated from them by a diastema, is a smallish, somewhat canine-like tooth, in both jaws. _Megalonyx_ and its allies are sometimes placed in a distinct family, MEGALONYCHIDAE. _Megalonyx_ itself had a skull very like that of _Bradypus_, being shorter and not so elongated as in the Mylodontidae. There is a strong tusk anteriorly, which is separated by a considerable space from the three molars lying behind it. Both pairs of limbs seem to have possessed five toes. This is a North American genus. It differs from the bulk of the American Edentates in having a complete jugal arch. _Megatherium_ is the type of yet a third family, MEGATHERIIDAE, of the Gravigrade Edentates. This creature is familiar from the many restorations which have been built up, and from its huge bulk, little short of that of an elephant. The skull, which is small for the size of the creature, has a complete jugal arch, from the middle of which depends a downward process as in other allied forms. The teeth grow to an extraordinary depth, and there are five of them in the upper and four in the lower jaw--on each side of course. The fore-limbs of the _Megatherium_ are very much more slender than the enormously bulky hind-limbs, upon which and the equally massive tail the animal seems to have supported itself while tearing down branches of trees, upon whose leaves it fed. In the scapula the acromion joins the coracoid as in _Bradypus_; the clavicle is large. The fore-limb is four-toed, and the hind-limb three-toed. The latter has but one clawed digit (the third, _i.e._ the inner). {184} On the manus, the three inner digits have powerful claws. This animal, too, was Pleistocene in time. The Megatheriidae had, however, small as well as gigantic forms. The genus _Zamicrus_ had a skull no bigger than that of a Sloth, while _Nothrotherium_ was also a comparatively small creature; the teeth of the latter genus are reduced to 4/3. The extinct group of the GLYPTODONTIDAE comprises large creatures with a dense covering of bony scutes which are arranged in a tesselated fashion, and thus form an immobile armature of immense strength. In correspondence with this massive carapace the dorsal vertebrae have fused together, and the lumbar vertebrae form a series ankylosed to each other and to the following sacrals. These creatures are all South American. [Illustration] FIG. 106.--_Glyptodon clavipes._ x 1/12. (After Owen.)