ANATOMY OF MEGAPTERA LONGIMANA. 31 



be observed that these diarthrodial joints occur on the ends of 

 that carpal cartilage which supports the great digit. 



On section, the separation of the ulnare and intermedium is 

 less striking along the proximal half of their articulation, but it 

 exists, and there are the usual surface grooves on both aspects. 

 No separation is visible between the pisiform and the epiphysial 

 cartilage of the ulna along the proximal § of their relation, but 

 the surface grooves are complete. A faint groove, or break, 

 appeared on the surface seeming to subdivide the very broad 

 ulnare into an ulnar and a radial portion, but as on section and 

 on slicing near the surface no trace of separation could be seen, 

 it was probably unnatural. 



CoTYiparison with the Carpal Bones of other Whales. — As I 

 hope to go into this subject fully in a subsequent paper, a short 

 statement may here suffice. Megaptcra differs from the other 

 finners, and from Mysticetus, in the enormous extent of the 

 ulnare (cuneiform bone), reaching as it does to opposite the 

 ulnar fourth of the carpal end of the radius, and expanding to 

 meet the short ulna. It is thus broader (10 inches) than 

 the intermedium (semilunar bone) and radiale (scaphoid bone) 

 together (about 4 inches each), and is also, from fore-arm to 

 metacarpus, the longest carpal cartilage. The ulnare in the 

 other finners does not reach to opposite the radius. The 

 two cartilages of the distal row (os magnum and unciform) 

 are much in the same position as in the other finners, but in 

 B. musculus the trapezoid bone, or cartilage, is present, though 

 not in B. borealis. The separation of the pisiform cartilage 

 from the epiphysis of the ulna is complete in B. borealis. In 

 the 50-feet-long B. musculus it is not so marked in the proximal 

 as in the distal half of the articulation, but it exists. I would 

 not regard the incomplete separation of the pisiform cartilage 

 as a character of Megaptera. It is the same in my half-grown 

 B. rostrata. 



The epiphysis of metacarpal V. in Megaptera might readily 

 be taken for a carpal cartilage, and when the bony metacarpals 

 are removed so might the epiphysis of metacarpal II. It is 

 notable that though digit II. is so much more massive in 

 Megaptera than in other finners, there is no trapezoid, much 

 less a trapezium, bone present in it. 



