372 R. S. Lull — Pleistocene Ground Sloth, 



Hind Limb. 



Femora. — Two femora, a right and left, are represented by 

 their diaphyses only, but the articular ends seem to have been 

 lost by breakage rather than by the removal of the epiphyses 

 through imperfect coossitication. One other right femur is 

 indicated by a little more than its distal half, with the articu- 

 lation fairly intact, and there is an additional internal condyle 

 from the left thigh. 



I am able to make a direct comparison of the femora only 

 with Owen's M. robustus. Allen describes rather briefly a 

 femur in his memoir on M. garmani but does not figure it. Two 

 of the Texan femora, Nos. 10264 and 10265, are smaller than 

 in M. robustus and lack the decided rugose character of the 

 latter,due in part doubtless to abrasion. The diaphyses are rather 

 featureless but show well the massive character of the bone. 

 They differ from M. robustus in that the lesser trochanter is 

 relatively small and in the sharper curve of the inner outline 

 of the bone, especially in its lower portion, implying apparently 

 a relatively wider distal extremity. The longitudinal ridge 

 shown by Owen to be parallel with the outer margin on the 

 anterior aspect is indicated in the right femur for about half 

 its length, but hardly at all on the left, while the subsidiary 

 ridges which limited the areas of attachment of the great thigh 

 muscles are lacking in each. The general contour of surface 

 aside from these minor irregularities is similar in all. The 

 distal end of the third femur is of greater size, but in its pres- 

 ent condition shows no points of contrast with that described 

 by Owen, nor am I able to compare with the data brought 

 out by Allen in his description. 



Dimensions of Cat. JVo. 1026J/.. 



Length over all, estimated 450 



" of diaphysis, as preserved 380 



Breadth across proximal end, estimated 240 



Least diameter of shaft, trans 120 



ant.-post. 57 



Breadth across distal extremity, estimated 210 



Dimensions of third femur, Cat. No. 10266. 



Breadth across distal condyles 185 



Width of intercondylar notch 50 



Tibim. — Two right tibiae are present, both in excellent pres- 

 ervation. They show the characteristic generic features in 

 marked degree — the shortness of the element compared with 

 its extreme width, and the proximal breadth, exceeding three- 

 quarters the entire length of the bone in M. robustus and in 

 one Texan specimen 7 while it is slightly less in, the other. 



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