176 



Biology in America 



the transition zone inclndo tlio mountain "lion" or puma, 

 whit'h extends liis j)ro\vIin<j: patli fi-oin I'atagonia to (-anada, 

 the Canada lynx, a skunk, the raeeoon, hadger and one of the 

 deer. Viee versa Canadian mammals extending across the 

 transition zone southward into the Sonoran include the chip- 

 munks, l)eaver. meadow mouse (Microtus) and the muskrat. 



Grove of Aspens Overflowed by a Beaver Pond 

 WiUi the (l.Miii and stumps cut by beaver in the foreyrouud. Original. 



Below the yellow pine forest on San Francisco IMountain 

 we reach the icgion of pinon pines and red cedars which ex- 

 tends between 6,000 and 7,000 feet, while below this we leave 

 the mountain and enter the desert. Both of these latter 

 areas belong to the southern or Sonoran life area in North 

 America, so named from the province of Sonora in ^Mexico, 

 which is at or near the center from which its characteristic 



