Mylodon harlani, from Rock Creek, Texas. 383 



three articulating facets for greater mobility in reaching 

 upward, a condition found in Megatherium but not in Mylodon 

 robushis, a grazing species of South America." 



I think Doctor Allen is correct in the assumption that 

 M. harlani and M. garmani show certain contrasting features, 

 and that the latter was the lighter and slenderer animal, but 

 I do not believe these points of contrast sufficiently great to 

 imply so marked a difference of feeding habits in creatures of 

 similar tooth structure. The "doctors disagree" also, for 

 Brown's arguments which prove Paramylodon a grazer have 

 not impressed Allen, who thinks that Paramylodon and 

 M. garmani are both browsers. The latter further believes 

 that M. harlani was a grazing type, which agrees with Brown's 

 statement, since Paramylodon and M. harlani are one, and not 

 with Allen's previously expressed view. I can not but feel 

 that the statement 1 have made above should apply equally to 

 all Mylodons and to Megatherium as well, though in the some- 

 what more generalized Mylodon an occasional variation, from a 

 strictly phytophagous diet might well have been possible when 

 opportunity or necessity arose. 



Relationships and Distribution. 



Mylodon represents the family Mylodontidpe, which, as Scott* 

 says, was numerously and variously represented in the Pleisto- 

 cene of South America, but much less so in that of North 

 America. The Mylodontidse also include the South American 

 genera Lestodon, larger than Mylodon ; Scelid other ium, the 

 smallest Pleistocene member of the family, with a narrow, 

 elongate skull ; Glossotherium, with an arched bony bridge 

 connecting the anterior end of the nasal bones with the pre- 

 maxillaries ; and Grypotherium, the hide of which has been 

 preserved in a cavern in Last Hope Inlet, Patagonia, and has 

 a thick covering of coarse hair and, within, a continuous armor 

 of small ossicles. Similar ossicles have been found at Rancho 

 La Brea, in fact, a number were contained in the matrix cling- 

 ing to the skull at Yale, and the inference is therefore that the 

 external covering of Mylodon was similar to that of Grypo- 

 therium. 



Geologically the Mylodontidae range back into the Santa 

 Cruz formation of South America, and Scott says further :f 



" There is evidence that at least two of the ground sloth 

 families, the Megalonychidse and the Mylodontidae, were distin- 

 guishable in the Deseado stage [Upper Oligocene], but 



* Scott, W. B., A history of land mammals in the western hemisphere, 

 p. 601, 1913. 



fOp. cit., p. 610. 



