360 B. S. Lull — Pleistocene Ground Sloth, 



lei with each other, and then approach and meet in the middle 

 line. They thus embrace a pit-like depression. This pecu- 

 liarity of structure is lacking in the modern sloths, and in all 

 the figures of Mylodon rohustus now available. Whether a 

 constant feature among the Texan types I can not tell, as but 

 one such symphysis is preserved. 



Dimensions. 



No. 10264, in which the centrum of lumbar one is not preserved. 



Sacrum, total length 515 mm 



greatest breadth (circa) 30 



2d lumbar, length of centrum 74 



width " " , ant. face 90 



height of centrum, ant. face . _ 6*7 '5 



height of neural canal 58 



width " " " ._. 57 



total height of vertebra, as preserved 232 



7th sacral, length of centrum _ 56 



width of centrum, post, face 82 



height" " " " 57 



" " neural canal* 30-5 



width " " " _ 55-5 



total height of vertebra 118*5 



Ilia, breadth over all __.1066 



Right ilium, ant. -post, diameter to margin of ace- 

 tabulum 480 



breadth _. 520 



width of acetabulum 125 



height " " 116 



Least distance between iliac crests . . _ 1 40 



Pelvic symphysis, ant.-post. diameter 82*5 



thickness at median line 65 



Ribs. 



A number of ribs were secured from the Mylodon quarry, 

 some twenty-seven in all. Of these at least four apparently 

 pertained to the young Elephas which was found in associa- 

 tion, while three others were clearly equine. This leaves 

 approximately twenty ribs which may be referred to Mylodon; 

 some other fragments may be the distal portions of certain of 

 those enumerated or may represent additional ribs. Of the 

 twenty which may pertain to Mylodon, about half are from 

 the left and half from the right side. 



The ribs are all characterized by small facets, the capitular 

 ones particularly, in contrast to those of the associated mam- 



* A median ridge along the floor reduces this height. Without the ridge 

 it is 36 mm . 



