Mylodon harlani, from Rock Creek, Texas. 369 



Ventrally, two-thirds of the scaphoid is articular, the remain- 

 ing third being the roughened under surface of the backward! v 

 projecting process just mentioned. Of the two facets, that for 

 the trapezoid is concave along one dimension and approxi- 

 mately flat along the other. It is sub-oval though somewhat 

 asymmetrical, full rounded on its anterior outline and slightly 

 concave on the posterior, while the magnum facet is of slightly 

 smaller area, and of approximately the same outline but con- 

 cave along all axes. 



Dimensions. 



Height of scaphoid No. 10265 40 mm 



Breadth .... _ _ 79 



Antero-posterior diameter 75 



Magnum. — A right magnum of approximately equivalent 

 size to the scaphoid and radius has been given the same cata- 

 logue number, 10265. It is an extremely irregular bone, of 

 which much of the surflcial area is covered by articular facets, 

 eight in all. Of these three are confluent on the inner, upper, 

 and outer aspects of the bone. The first of these, the scaph- 

 oidal facet, is a pronounced, somewhat conical curve, fully 

 convex in the antero-posterior diameter, slightly so in the 

 transverse. This bounds the lunar facet, the largest of all, 

 from which it is separated in part merely by a ridge, elsewhere 

 by a slight groove with elevated margins. The lunar facet is 

 flat along one side with a continuous curve embracing the 

 others, so that it is rather more than a semi-circle in area. It 

 is convex, with a tendency toward concavity along certain of 

 its borders. The unciform facet bounds the lunar articulation 

 along the straight side and is a long, narrow area with a sinuous 

 outline. Adjacent to this is the large facet, sub-triangular in 

 shape and somewhat concave, with which the third metacarpal 

 articulated, while adjoining this is the small articulation of the 

 second metacarpal. 



Both of these carpal bones have approximately the same 

 form as in Mylodon robustus but may differ in details and pro- 

 portions. My only means of comparison, however, is with the 

 flgures of the assembled manus given by Owen, which show 

 but two aspects of each bone, making adequate comparison 

 difficult. 



Dimensions of magnum. 



meter 



Antero-posterior diameter 57 5 



Height 47 mm 



Transverse diameter _. 55 



