THE PELVIC LIMB 



noteworthy features consist of the hairy sole, or at least that it is as 

 hairy as the dorsal part of the foot; the retention in all (apparently) 

 genera but Mirounga of sharp nails of fair size when there seems to be 

 no use to which they could be put, the fact that the first and fifth digits 

 are longer than the others, while the third is the shortest, giving to the 

 pes when expanded a lunate shape comparable to the tail of a fish or 

 whale; and the expected fact that the webbing between the toes is 

 complete. 



The foot of the seal has retained its proportional length in relation 

 to body length, as judged by such a terrestrial carnivore as the cat, and 

 therefore has not suffered the marked shrinkage experienced by the 

 shank and, especially, the thigh. In a partly dissected specimen of 

 Phoca hispida the tendency of the feet was to adopt a position with 

 soles not strictly parallel but with the upper (outer) borders slightly 

 converging, but in the live animal this seems to be overcome by muscle 

 or other tissue tension so that the soles are perfectly parallel. From a 

 trailing position of the feet, movement through the ankle joint proper 

 is apparently only about 30 degrees, but greater freedom is allowed by 

 means of the articulations of the astragalus and calcaneum with the 

 centrale and cuboid, this amounting to about 65 degrees. As a result 

 the tarsus may be flexed approximately at a right angle and by this es- 

 sentially hand-like action one foot is enabled to follow through and aid 

 by its medial motion the lateral movement of the opposite foot while 

 executing a swimming impulse. This tarsal joint, as it may be called, 

 also enables the animal to progress very slowly by a manner first called 

 to my attention by Breder (MS) and since observed personally. With 

 feet palm to palm these members are flexed through the tarsal joints, the 

 tips of the digits remaining together. The feet are then abruptly ex- 

 tended, imparting a gentle though definite forward impulse to the en- 

 tire body. This cannot be strong enough, however, to constitute a use- 

 ful accomplishment. 



No great significance can be attached to details of the phocid tarsal 

 bones, other than that already mentioned and the extension of the 

 astragalus, discussed later. It is somewhat narrow, however, and thus 

 sidewise (horizontal to the sole) motion is facilitated through looseness 

 of the tarsal articulations. This tarsal narrowing causes a crowded, some- 

 what overlapping condition of the proximal metatarsi. Spreading of 

 the toes, in this animal at least, seems to be facilitated by an arrangement 

 of the joints whereby this is accomplished by a partially oblique ex- 

 tension of the first digit and a slight flexion of the fifth, this being com- 



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