THE SEA-OTTER AND ITS EXTERMINATION 219 



of an ordinary otter. The skin invests the body as loosely 

 as a pillow-case covers a pillow ; and the dark brown fur 

 is unrivalled for its softness, depth, and density. But 

 even more remarkable is the difference between the cheek- 

 teeth of the two animals. In place of the sharply cusped 

 grinders of the common otter, the marine species has the 

 crowns of these teeth surmounted by smooth ill-defined 

 bosses, separated by narrow crack-like lines ; the one type 

 having been aptly compared to freshly chipped flints, and 

 the other to water-worn pebbles. Clearly such structural 

 differences must be correlated with a totally different 

 description of diet, and, in place of being a fish-eater, 

 the sea-otter subsists by grinding up sea-urchins, clams, 

 mussels, and such-like, shells and all. 



Had we living animals alone to guide us, there might 

 be some hesitation in saying that the sea-otter is a highly 

 modified offshoot from the stock of the ordinary otter, but 

 the evidence of extinct forms indicates the probability of 

 this being the case. Fossil remains of true otters occur 

 comparatively low down in the series of rocks belonging 

 to the Tertiary period ; and somewhat higher in the scale 

 are found, both in Europe and India, those of an extinct 

 genus {Enhydriodon), in which the cheek-teeth are to a 

 certain extent intermediate between the types respectively 

 characteristic of the ordinary and the sea-otters. These 

 intermediate extinct otters appear, however, to have been 

 fresh-water animals, so that purely marine habits would 

 seem to have been acquired only with the advent of the 

 modern sea-otter. 



The geographical range of the latter on the American 

 side formerly included Alaska, the Aleutian and Pribiloff 

 Islands, Sitka, and Vancouver Island, and thus down 

 the coast to California; while on the opposite shore it 



