176 Biology in America 



the transition zone include the mountain "lion" or puma, 

 which extends his prowling path from Patagonia to Canada, 

 the Canada lynx, a skunk, the raccoon, badger and one of the 

 deer. Vice versa Canadian mammals extending across the 

 transition zone southward into the Sonoran include the chip- 

 munks, beaver, meadow mouse (Microtus) and the muskrat. 



GROVE OF ASPENS OVERFLOWED BY A BEAVER POND 

 With the dam and stumps cut by beaver in the foreground. Original. 



Below the yellow 

 we reach the region 

 tends between 6,000 

 the mountain and 

 areas belong to the 

 America, so named 

 which is at or near 



pine forest on San Francisco Mountain 

 of piiion pines and red cedars which ex- 

 and 7,000 feet, while below this we leave 

 enter the desert. Both of these latter 

 southern or Sonoran life area in North 

 from the province of Sonora in Mexico, 

 the center from which its characteristic 



