540 MANUAL OF ZOOLOGY SECT. 



at their bases ; or relatively short and blunt, when they are 

 incompletely or not at all retractile. The otters (Lutra} 

 differ from the rest in having short limbs with the toes 

 connected by webs of skin. 



The Pinnipedia, or seals and walruses (Fig. 326), have 

 the proximal segments of the limbs short, so that the arm 

 and thigh and nearly all the fore-arm and leg are enclosed 

 in the common integument of the trunk, and the manus and 

 pes elongated. The earless seals (Phocida) are much more 

 completely adapted to an aquatic life than the eared seals 



FIG. 326. Harbor Seal (Phoca vitulina). 



{Otariidcz} and walruses (Trichechida) , being unable to flex 

 the thigh forwards under the body, so that the hind-limbs 

 may aid in supporting the weight, and thus being only able 

 to drag themselves along very awkwardly when on dry land. 

 The pinna of the ear is absent in the earless seals and 

 walruses, well developed in the eared seals. The surface in 

 all is covered with a thick soft fur. In the fur seals there 

 are two kinds of hairs, those of the one kind being longer 

 and coarser and scattered through the more numerous shorter 

 and finer hairs composing the fur proper. A remarkable 



