772 MAMMALIA. 



(2220.) The distribution of these tyrants of the animal creation we 

 shall find to be coextensive with that of the victims they are appointed 

 to destroy. 



(2221.) The aquatic tribes of the CAEBTIVORA (Amphibia, Cuv.) are 

 obviously constructed for swimming. Their bodies, covered over with 

 short, close, and polished hair, taper off towards each extremity, re- 

 sembling in form those of the CETACEANS. The cervical, thoracic, and 

 lumbar regions of the spine are light and flexible ; and the pelvis is con- 

 tracted, and placed as far back as possible. Both the anterior and pos- 

 terior extremities, although completely formed, are short, and in the 

 living animal are only free externally as far as the carpal and tarsal 

 joints. The feet, moreover, are broadly webbed, and thus become con- 

 verted into most efficient paddles, by the aid of which these creatures 

 swim with astonishing ease and elegance, the hinder pair performing at 

 once the functions of oars and rudder. Upon land, however, their 



Fig. 392. 



Skeleton of the Seal. 



movements are, as might be supposed, extremely clumsy : it is true that 

 they not unfrequently scramble on to the beach, there to bask in the 

 sun, or to suckle their little ones ; but if danger threatens, they imme- 

 diately take to the water, and fall easy victims if their retreat towards 

 the sea be intercepted. 



(2222.) Such being the helplessness of the Seals when they quit the 

 water for the shore, it is not surprising that, in some of the larger and 

 more unwieldy forms, assistant locomotive organs have been given, 

 derived from unlooked-for sources. Thus in the Walrus (Trichechus 

 rosmarus), which apparently obtains nourishment from the fuci of the 

 shore, as well as by destroying living prey, even the canine teeth of the 

 upper jaw are converted into instruments of progression, and serve as 

 crutches to drag the animal along. In these creatures the upper jaw 

 is extremely dilated and massive, and the canine teeth implanted in it 

 not unfrequently project downwards to a distance of from one to two 



