460 



W. F. BLAIR 



bution of the Peromyscus maniculatus species group of 



Fig. 11. Distri^^.,-.. 

 mice (from Blair, 1950) 



quently across the central area from which warmth-adapted species 

 are indicated to have been driven. Such species as the cotton rat 

 {Sigmodon hispidus) , cottontail {Sylvilagus floridanus) , coachwhip 

 {Masticophis flagellum), and green treefrog {Hyla cinerea) are 

 representative. Their wide distribution can be explained as having 

 been attained by spread from an eastern or western refuge or by 

 such a rapid spread from both refuges that contact of populations 

 and interbreeding were reestablished before marked differentiation 



