No. I.] 



OSTEOLOGY OF PCEBROTHERIUM. 



65 



the head, higher, indeed, than in Pcebrotherium, terminating in 

 a long, massive, and incurved hook. The internal tuberosity is 

 increased in size, and the bicipital groove becomes very much 

 wider, occupying nearly half the width of the proximal end, and 

 the rudimentary bicipital tubercle of Pcebrotherium has become 

 a prominent ridge dividing the groove 

 into two parts. 



The radius, though still slender, is 

 much broader and more flattened 

 than in the White River genus, and 

 has received the inward curvature of 

 the recent forms ; the head is ex- 

 panded, especially towards the outer 

 side ; the distal end has also expanded, 

 and the carpal facets are no longer 

 of equal width, that for the cuneiform 

 being now the broadest. The shaft 

 of the ulna is still further reduced, 

 and is no longer visible from the 

 front, except just above the distal 

 end. The interosseous foramina pen- 

 etrate, as in PcebrotJierium. The ole- 

 cranon is not so high, and projects 

 more strongly backward than in the 

 latter, but it descends more steeply 

 from the coracoid process. 



In the carpus (PI. Ill, Fig. 52) the 

 scaphoid has become more massive 

 and broader in front, producing a 

 notch on the internal side. The lunar is relatively narrower ; 

 its distal beak is less prominent, the magnum and unciform 

 facets being more nearly equal and inclining to each other at 

 a more open angle. The cuneiform is heavier and wider and 

 'is less excavated upon the outer side for the descending distal 

 end of the ulna. The pisiform is more thickened and increased 

 in depth. No facets on the scaphoid or trapezoid indicate the 

 presence of the trapezium, though it may have been preserved. 

 The trapezoid is larger than in PcebrotJierium ; the magnum is 

 higher in proportion to its breadth ; the lunar surface is broader 

 and less oblique. The unciform, on the other hand, has become 



Fig. E. 

 Humerus of Procamelus occiden- 

 talis ; anterior view of proxi- 

 mal end (after Cope). 



