17-2 



SKETCH OF THE HISTORY OF MAMMALIA. 



as not to interrupt the gradual decrease. The spine is 

 provided with muscles capable of inflecting: it with con- 

 siderable force. The clothing consists of short, stiff, 

 glossy hairs, very closely set, and adpressed against the 

 skin. The limbs are oars or paddles. The anterior pair 

 have the humerus and fore arm so short, that little more 

 than the paw alone advances from the body ; this in 

 reality consists of five fingers, but they are impacted in 

 skin, the nails, which are flat, indicating their number. 

 The hinder limbs are directed backwards, and terminate 

 the body ; the bones are short and strong, and the hip- 

 joints want the ligamentum teres. The feet are broad- 



112.— Skeleton of Seal. 



webbed paddles, consisting of five toes, the central of 

 which is the shortest, the outer one on each side the 

 longest ; when not in action the webs of these ])addles 

 are folded, and the toes in contact, but when brought 

 into use they spread and present a broad surface. Between 

 these paddles is the short and compressed tail. On land 

 or masses of ice these animals are very awkward and 

 clumsy, but they scuttle along by the action of the an- 

 terior paddles, dragging their hinder quarters after them, 

 and manage to proceed with tolerable rapidity ; they 

 cap also climb rocks and crags of ice. 



The neck in these aquatic animals is very long and 



