

MEGA THERIIDAZ 



1S9 



Fig. 63.— Skeleton of Mylodon rolnistvs (Pleistocene, South 

 America). From Owen. 



the feet differ considerably from those obtaining in the type genus. 

 S. l&ptoc&plmhim, 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 he taken to 

 include a number 

 of comparatively 

 large Edentates, 

 some of which have 

 been described 

 under the names of 

 Grypotherium, Lest- 

 odon, and Pseudo- 

 lestodon. The teeth 

 of the upper jaw 

 are generally of an 

 oval or subtriangu- 

 lar 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 corre- 

 sponding age in Kentucky. The Patagonian M. {Grypotherium) 

 darwini is a remarkable form, characterised by the presence of a 

 bony arch connecting the premaxillaB with the nasals, of which, as 

 already mentioned, there is an incomplete development in 

 Megatherivgn. 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. NothrotheHum 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, Bernhardt, 

 and others. 



Promegathenum. — Two genera from the infra-Pampean beds 



