Smithsonian Report, 1923. — Grinnell 



Plate 2 



Illustrates the Way in Which the Burrowing Rodents Turn Over 

 the Soil, a Light-Colored Sand From Below Is Deposited, Uncon- 

 formably, on top of the dark-colored surface stratum. the 

 Pocket Gopher Here Concerned Was Thomomys perpallidus perpes 



Photo taken by J. Grinnell June 21, 1911, near Onyx, Kern County, California 



2. I n This Case a Stony Substratum Is Brought to the Surface Where 

 Its Rate of Weathering Will Be Hastened; in Other Words, the 

 Presence of Burrowing Rodents Is Accelerating the Process of 

 Soil Formation and This, in Course of Time, Will Mean Improve- 

 ment in the Crop of Native Grasses or Other Plant Growths. 

 The Pocket Gopher Responsible for this Work Was Thomomys 

 bottae minor 



Photo taken by J. Dixon December 12, 1917, near Gualala, Mendocino County, California 



