ANATO.AIY OF MEGAPTERA LONGIMANA. 59 



laxity of the ligamentous connections of the femur in Megaptera, 

 compared with those of Mysticetus and B. musculus, is striking. 

 20. Function. — The more the connections of the femur in 

 Megaptera are examined the less easy does it seem to give a 

 functional explanation of its presence. It might be looked on 

 as serving a sesamoid function, but it does not play on cartilage, 

 and does not give the mechanical advantages of a sesamoid. 

 It has even less muscular connection than the small oval femur 

 in my 50-feet-long B. musculus. Mysticetus has also a rudi- 

 mentary tibia, Megaptera a femur only, B. musculus a still more 

 rudimentary femur, and B. borealis, as I find, none at all. 



21. EXPLANATION OF PLATES ITL, IV., and V. 



Fig. 6. Left paddle of Megaptera, flexor aspect, reduced to -^. 

 The epiphyses of the luunerus and fore-arm are seen. The epiphyses 

 of the fore-arm and metacarpal bones, at the carpiis, are to be dis- 

 tinguished from the carpal bones proper. The causes of the nine 

 nodes on the radial border, shown in Part I., Plate I., are seen ; 

 and of the minor undulations on the ulnar border, near the tip. 

 The fitting of the alternating nodes and hollows of the digits, the 

 position of the joint in the nodes, and of the joints in the terminal 

 cartilages, are represented. 



Fig. 7. Left scapula of IMegaptera, turned round to show the dorsal 

 surface, with its very low spine, s. /' prescapular fossa ; a, anterior 

 angle ; ^:>, posterior angle ; c, rudimentary coracoid ; e, low elevation ; 

 reduced to -^. 



Fig. 8. View of glenoid cavity of same scapula, c, rudimentary 

 coracoid, not yet completely luiited to the scapula. 



Fig. 9. Dorsal view of section of left cai'pus of Megaptera with 

 portions of radius and ulna and their epiphyses, and portions of the 

 metacarpal bones and the epiphysis of each ; reduced to -~^. r, 

 radiale ; i, intermedium ; «, ulnare ; p, pisiform ; 3, os magnum ; 

 4, unciform bone. Ossification is seen in the radiale and ulnare, and 

 in the epiphysis of the radius and of the ulna. These ossifications 

 are seen only on section. The dotted line is where the pisiform and 

 the epiphysis of the ulna are not completely separate. The proximal 

 synovial cavity at the os magnum, 3, is represented. 



Fig. 10. Terminal cartilage, with distal phalanx, of digit III.; a, 

 the joint in the cartilage ; reduced to J-. 



Fig. 11. Terminal cartilage, with part of distal phalanx of digit II. 

 (Index digit), a, its first joint; b, its second joint, lieduced to \. 



Fig. 12. Longitudinal vertical section of the terminal cartilage of 

 digit II., showing the two joints a and b ; the proximal reaching both 

 surfaces ; the distal seen only on section ; reduced to J. The flexor 

 aspect of fig. 12 is that next to fig. 11. The radial border of figs, 

 10 and 11 is towards fiff. 12. 



