GEOGRAPHIC DISTRIBUTION 



313 



northern jumping mouse, three-toed woodpecker, and spruce grouse. 

 The open treeless areas of the west are inhabited by the prong-horn 

 antelope, bison, ground squirrels and many others. So nearly are many 

 of these animals limited to one type of vegetation area that it is difficult 



iGlaucomys Sabrinus 

 IGlaucoinys Volana 



Fig. 268. — Ranges of the North American flying squirrels, Glaucomys volaiis and G. sa- 

 brinus. {After Howell, "North A7nerica?i Fauna," No. 44.) 



to avoid concluding that the conditions prevailing in such areas are 

 paramount in their lives. Sometimes the maps of ranges of forest 

 animals and of prairie animals appear to overlap, as if the vegetation 

 were not of great importance. In one such case, however, the appear- 



