278 VERTEBRATA 



a remarkable variation in the color of its fur. While ordi- 

 narily of a reddish hue it occasionally varies to a jet black. 

 The red skin is valued at only one or two dollars, but a 

 black one sometimes sells for as much as two thousand 



FIG. 315. Polar bear (Thalarctosmaritimus). Photographed in the Philadelphia 

 Zoological Gardens. 



dollars. The gray fox is confined to the more southern 

 portions of the United States. 



The marten family (Muslelidce) includes the fish-loving 

 otter, slender-bodied mink and weasel, the marten, skunk, 

 and badger, all of which are valuable fur-bearing animals. 

 The weasel and mink are destructive to poultry, but the 

 weasel atones for his evil by terrorizing the rats and mice. 



