1915.] 



II^TEODUCTION-. 



27 



T. monticola meets the various forms of the hottse group along the west 

 slope of the Sierra Nevada, and other species along the east slope of 

 the range, the hne of demarcation seems to be sharp, without actual 

 overlapping of the species, although one form may lap well past the 



B205a-122 



Fig. 9. — Map showing distribution of certaia species and subspecies of Thomomys, and localities at whicli 



specimens were collected. 



1. umhrinus. 



2. orizahx. 



3. peregrinus. 



4. atrovarius. 



5. sheldoni. 



6. nelsoni. 



I. goldniani. 

 i. perditibs. 



other in close juxtaposition, showing an apparent but not real over- 

 lapping of range. The two forms generally occupy different hfe 

 zones, or different types of ground, or else divide the territory on 



