LETTER OF TRANSMITTAL. 



United States Department of Agriculture, 



Bureau of Biological Survey, 

 Washington, D. C, April 29, 1915. 



Sm: I have the honor to transmit herewith for pubUcation as 

 North American Fauna No. 39, a revision of the pocket gophers of 

 the genus TTiomomys, by Vernon Bailey, chief field naturalist of the 

 Biological Survey. 



Pocket gophers are burrowing rodents which in pursuit of food 

 and in running tunnels often damage crops, young trees, and irriga- 

 tion ditches. Moreover, the heaps of earth ejected from the tunnels 

 not only cover more vegetation than the animals eat, but also obstruct 

 the operation of mowing machines. Gopher burrows frequently 

 penetrate and cut through irrigation-ditch banks, and the escaping 

 water becomes a menace to agriculture and sometimes to human life. 

 The animals are thus of considerable economic importance. 



The present paper completes the technical revision of the pocket 

 gophers (family Geomyidse), the first part of which was prepared by 

 Dr. C. Hart Merriam and published in 1895 as North American 

 Fauna No. 8. The revision will supply definite information regarding 

 the status and geographic distribution of the several forms, which is 

 important in connection with attempts to control or exterminate 

 them. 



Respectfully, 



Henry W. Henshaw, 

 Chief y Biological Survey. 



Hon. David F. Houston, 



Secretary of Agriculture. 



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