158 SKELETON OF THE SEAL. 



applied to clasp the young ; and the animal so observed, 

 with its own head and that of its young above water, has 

 given rise to the fable of the siren and mermaid. The 

 bones and joints of the pectoral fin are accordingly better 

 developed than in the ordinary whales. The first row of 

 carpal bones, 56, consists of two — one articulated to the 

 radius, 55, the other to the ulna, 54, and fifth digit, 57, v, 

 and both to the single bone representing the second row. 

 The first digit, ?*, consists of a short metacarpal ; the me- 

 tacarpals of the others support each three phalanges. 



SKELETON OF THE SEAL. 



In the seal tribe {Phoci(ice), another and well-marked 

 stage is gained in the development of the terrestrial in- 

 struments of locomotion. Hind limbs are now added — 

 the marine mammal has become a quadruped. The 

 sphere of life of the seals is near the shores; they often 

 come on land ; they sleep and bring forth among the 

 rocks and littoral caves : hence the necessity for a better 

 development of the pectoral limbs, although these, like 

 the pelvic ones, still retain the general form of fins. The 

 fish-hunting seals make more use of the head in inde- 

 pendent movements of sudden extension, retraction, and 

 quick turns to the right and left, than do the cetacea of 

 like diet ; and the walrus (Fig. 27) works the head, as the 

 place of attachment of its long, vertical, down-growing 

 tusks, in various movements required in climbing over 

 floes and bergs of ice. Accordingly, in the seal tribe, we 

 find the seven neck-vertebrae (^tb.) c, longer, and with more 

 finished and free-playing joints than in the whales and 

 dugongs. The sigmoid curve, in which they can be 



