ANATOMY OF MEGAPTERA LONGIMANA. 47 



B. musculus. They were, on the internal aspect, three, a flexor 

 digitorum ulnaris, a flexor digitorum radialis, and the flexor 

 carpi ulnaris ; on the external aspect, one, an extensor com- 

 munis digitorum. The proportions of the two flexors of the 

 fingers were reversed, as compared with those of B. musculus, 

 the ulnar flexor being about a third the size of the radial flexor, 

 instead of larger than it, as in B. musculus. 



The account of these muscles in Megaptera may be shortened 

 by referring to the figures which I gave of them in B. mus- 

 culus, here reproduced in Plate IV. figs. 13 and 14 ; and 

 reference may be made to my detailed account of the muscles 

 in B. musculus (this Journal, 1871). It was a mature B. mus- 

 culus, 64 feet long, the pectoral fin 7 feet 8 inches long, the 

 longest digit 33 J inches in length ; while in this Megaptera the 

 pectoral fin was 12 feet long, the longest digit 81 inches in 

 length. 



Flexor carpi ulnaris. Belly does not spread like a fan as 

 it does in B. musculus, but is thick and fusiform from the 

 origin onwards. Origin entirely on the cartilaginous olecranon, 

 abruptly from its distal edge, the aponeurosis reaching for about 

 J inch forwards. Fleshy for 11 inches, being nearly half the 

 length. Thickness of flesh at origin fully 1 inch, at middle 

 | inch. Belly covered by a thick aponeurosis of origin. Tendon 

 of reception is continued on deep aspect of belly. Length of 

 fleshy bundles about 1 inch, running obliquely between the 

 two aponeuroses. The tendon, after 4 inches from the belly, is 

 elliptical in section, lies edgeways to the ulna, is 1J inch from 

 the ulna, the total distance here from the ulna to the free 

 upper border of the paddle, 6 inches. Tendon lies in a strong 

 sheath, which also covers the belly, distinct from the aponeur- 

 osis of origin, and goes down to the upper border of the ulna. 

 This is the strong fibrous curtain which I noted in B. mysti- 

 cetus, absent in B. musculus. The blubber between the tendon 

 and the free border of the paddle is much mixed with fibrous 

 tissue, in longitudinal streaks. Distally the tendon gradually 

 gets nearer the ulna, narrowing the fibrous curtain, expands in 

 the last 3 inches, and is inserted entirely into the proximal 

 border of the pisiform cartilage, not reaching quite up to the 

 angle of the pisiform. The tendon at 4 inches from the flesh 



