594 THE CARNIVORES 



Pliocene, while it is not till the succeeding period that they became abundant. 

 This late appearance of the bears is in harmony with what we have already stated 

 as to their specialization. 



With the exception of the Indian sloth-bear and a peculiar species from Tibet, 

 all the bears are now generally included in the genus Ursus. This genus is charac- 

 terized by having a total of forty-two teeth (when all the small premolars are pres- 

 ent), of which f are incisors, \ canines, \ premolars, and f molars on each side. 

 In the adults, as already mentioned, several or all of the three anterior premolars 

 may disappear from both jaws, although the one immediately behind the tusk may 

 remain longer than the others. The molar teeth are characterized by their crowns- 

 being longer than they are broad ; the last upper molar being a much elongated 

 tooth, while in the lower jaw the last molar is shorter than the tooth which pre- 

 cedes it. As a rule, the soles of the feet are naked ; and the claws are of moderate 

 length and curvature. As in the other genera of the family, the ears are small, 

 erect, and thickly haired ; and the pupil of the eye is round. The geographical 

 distribution of the genus is coextensive with that of the family. 



THE POLAR BEAR (Urszis maritimus) 



Not only does the Polar bear differ from all other bears by its pure white coat, 

 but it is also distinguished from the greater number of white Mammals in that this 

 color is retained at all seasons of the year, instead of being exchanged in summer 

 for a darker tint. In addition to this distinctive white coloration, the Polar bear is 

 further characterized by the relatively-small size and extremely-elongated form of 

 its head, as well as by the molar teeth being relatively smaller and narrower than in 

 the other members of the genus. Moreover, the soles of the feet have a certain 

 amount of hair growing upon them, doubtless for the purpose of enabling the ani- 

 mal to have a better hold upon the ice. The neck is also longer than in other bears, 

 while the ears are unusually small. It is one of the largest members of the group, 

 not unfrequently attaining a length of close upon nine feet, although exact 

 measurements from recently-killed wild examples are but few. 



The Polar bear is found throughout the Arctic regions of both Hemispheres. 

 It is now rare on the southwestern coasts of Spitzbergen and Nova Zembla,. 

 where the ice almost completely disappears in summer. According to Baron Nor- 

 denskjold, it is more common on the northern parts of those islands, where there i& 

 perpetual ice. On the north coasts of America and Asia it is found everywhere, 

 and becomes more and more numerous as we travel northward. In Labrador, 

 where it is now very rare, there is evidence that it was once comparatively common, 

 and Dr. A. S. Packard is of opinion that its range originally extended even down 

 into the State of Maine. The white bears seen by John Cabot in the year 1497 are 



