ART. ir, A>7AT0MY OP THE EARED AND EARLESS SEALS HOWELL 129 



Zalophus were emaciated and those of the Phoca very full, little com- 

 parison of the strength of the shank muscles could be made. Details 

 of note, however, were the presence in Phoca only of a gastrocnemius 

 lateralis and absence of the soleus, and strength of the gastrocnemius 

 medialis and flexor hallucis longus. These differences are, of course, 

 related to variations in foot action, but most of them in an obscure 

 manner. 



The effective length of the bony part of the foot, measured from 

 the posterior margin of the astragalar condyle for a cat, is 34, the 

 Zalophus 28, and Phoca 34 per cent of the body length. Thus the 

 osseous foot of the last has not shrunken in relation to the trunk 

 length as has the rest of the limb, and that of the otariid has done 

 so but slightl}^ Or from a more likely aspect, the foot of both ani- 

 mals has experienced a secondary increase in size following a very- 

 marked, primary decrease in the length of the rest of the limb, 

 especially the femur. This increase of foot length, however, has 

 not been sufficiently rapid in the Otariidae to keep pace with the 

 needs of the animal, and there has been an extension of the digits by 

 means of cartilagenous rods and slightly more circumscribed inter- 

 digital membranes. The part of the pes distad of the bones is very 

 flexible and the cartilages are prolonged distad of the interdigital 

 membranes to a degree that seems entirely useless, and one which at 

 present seems very inefficient. 



The measurement from the tip of the longest otariid toe (exter- 

 nally) to the border of the astragalar condyle is 36 per cent of the 

 body length, which is the same as in the phocid. In the latter, how- 

 ever, the interdigital membrane extends between the toes in a much 

 more effect've manner, and there is no flexibil'ty distad, for there 

 are no cartilagenous extens'ons of the digits. But the foot is rela- 

 tively larger than in the otariid, and the measurement from the 

 external toe tip, as above, constitutes the same proportion of the 

 trunk length as in the eared seal. Either the increase in foot size 

 has kept pace with the needs of the animal, or, as seems by no means 

 unlikely, the Phocidae lack the ability so readilj^ to develop digital 

 cartilages. 



As with the manus the plantar surface of the otariid is bare and 

 wrinkled, and of the phocids, as well haired as the remainder of the 

 foot. The first and fifth toes of the former animal have minute 

 nails, sunk in pits of the integument, but the nails of the other three 

 digits are long, nearly straight, and very slender, as are those of all 

 five digits of the phocid. The otariid frequently folds back the 

 part of the pes distad of the bones, leaving the three long nails pro- 

 jecting, and with these vigorously scratches all parts of the body. I 

 see no other way in which they could be utilized and agree with F. 

 "Wood Jones (1925) that the retention of real nails upon the three 

 86377—28 



