28 PROFESSOR STRUTHERS. 



proximal third, expands greatly in breadth towards its carpal 

 end, and is thicker throughout. At the carpal end the breadths 

 are llf inches in Megaptera, in this full-grown B, musculus 

 only 8f . This expansion in Megaptera renders the lower border 

 of the radius very concave along its distal half or third. In the 

 50-feet-long B. musculus there is very little concavity there; 

 in my 64-feet-long B. musculus (this Journal, 1871), the 

 concavity is more marked, and most so just below the middle 

 of the bone, but is not to be compared to the great concavity 

 towards the wrist in Megaptera. In the Qb to 66-feet-long 

 B. musculus the radius is convex throughout on this border, 

 except just after the proximal end.^ 



Ulna. — The differential characters of the ulna in Megaptera 

 are, the much shorter and much less expanded olecranon, its 

 shortness at the carpal end compared with the radius, the more 

 bent shaft, and the greater expansion at the carpal end. The 

 breadths at the wrist are in Megaptera Ih inches, in the 65 to 66- 

 feet-long B. musculus 6|. The ulna falls short of the radius at 

 the wrist, in Megaptera by 3 inches, in this B. musculus by 

 1^ inches. The hony olecranon in Megaptera is a short blunt 

 process projecting 1 to 1| inches beyond the humerus, with an 

 abrupt oval end, 3 inches in length, 2i in thickness. In this 

 65 to 66-feet-long B. musculus, it projects 5 inches beyond the 

 humerus and expands to a breadth of 12| inches. In the 50- 

 feet-long B. musculus, the bony olecranon projects 2| inches, 

 and expands to a breadth of 7 inches, the future recurved part 

 represented as yet only by cartilage. In the 65 to 66-feet-long 

 B. musculus this great bony olecranon reaches for 5 inches 

 along the ulnar border of the humerus, forming a nearly 

 rectangular socket for this part of the elbow-joint ; in Megap- 

 tera not at all, leaving the here recurved epiphysis of the 



1 By the. above characters I am able to recognise a large cetacean radius which 

 came to Leith some years ago in a cargo of guano, as that of a full-grown 

 Megaptera. Length, epiphyses consolidated, 37 inches ; breadth at wrist 12, 

 probably 13 inches, as it is somewhat injured here ; thickness at wrist, 7 inches. 

 On section it is seen that there is no medullary canal, but cancellous tissue 

 throughout. The cancelli are more open at the second quarter of the bone than 

 at any other part. There is a layer of dense tissue at the radial end, -4 to J 

 inch thick ; and along the middle half of the shaft the tissue may be termed 

 dense for 4 to f inch at the surface, but not quite dense, and with gradual 

 transition to the cancellated part. 



