_Scelidotherium_, _Mylodon_, etc.—Of the more important remaining genera of this family a briefer notice will suffice. _Scelidotherium_ (in which _Platyonyx_ may be included) comprises several species of considerably smaller dimensions than the Megatherium, and is in some respects intermediate between that genus and _Mylodon_. The teeth have an oval cross-section, like those of the Sloths, while the skull, in which the length of the nasals is subject to great variation in the different species, approximates more or less closely to that of the _Myrmecophagidæ_. The humerus generally has an entepicondylar foramen; and the form and relations of the bones of the feet differ considerably from those obtaining in the type genus. _S. leptocephalum_, the type of the genus, occurs in Patagonia and Argentina but other species are found in Brazil and Chili. The genus _Mylodon_, in its widest sense, may be taken to include a number of comparatively large Edentates, some of which have been described under the names of _Grypotherium_, _Lestodon_, and _Pseudolestodon_. The teeth of the upper jaw are generally of an oval or subtriangular section; and in the more typical forms the first and second teeth are separated by a short interval, the former being horizontally worn. In other species, however, like _M. (Lestodon) armatus_, there is a considerable space between the first and second teeth, and the first is worn obliquely. The skull is exceedingly like that of the Sloths in general contour; and there is not the descending process at the angle of the mandible found in _Megatherium_. The humerus has no entepicondylar foramen. The species represented in Fig. 63 is from the Pleistocene of South America; but the type of the genus is _M. harlani_, from beds of corresponding age in Kentucky. The Patagonian _M. (Grypotherium) darwini_ is a remarkable form, characterised by the presence of a bony arch connecting the premaxillæ with the nasals, of which, as already mentioned, there is an incomplete development in _Megatherium_. _Megalonyx_, from the Pleistocene of Kentucky, differs from _Mylodon_ by the long interval between the first and second teeth, and also by the presence of an entepicondylar foramen in the humerus. _Nothrotherium_ is a smaller form, occurring in the deposits of the Brazilian caves, of which the dental features have been already mentioned. The osteological characters of these and other allied genera have been fully described in the works of Cuvier, Owen, Burmeister, Leidy, Ameghino, Gervais, Reinhardt, and others. [Illustration: FIG. 63.—Skeleton of _Mylodon robustus_ (Pleistocene, South America). From Owen.] _Promegatherium._—Two genera from the infra-Pampean beds of Argentina, described as _Promegatherium_ and _Promylodon_, are respectively distinguished from _Megatherium_ and _Mylodon_ by the presence of bands of enamel on the teeth, which points to the descent of the Edentates from mammals with enamelled teeth.