1915.] 



INTEODUCTION. 



31 



localities. The distribution maps show many wide areas in which 

 no gophers have been collected and in which the resident species is 

 still unidentified. 



The character of the specimens has generally been such as to 

 render the study most profitable. Well-made skins with cleaned 

 skulls, in series suJB&cient to show variation due to sex, age, and 

 abnormahties, have greatly simplified the task of classification. 

 The skulls of a few specimens collected on early expeditions have 

 been removed and cleaned and for the first time studied in relation 

 to ample material. In this way errors in the former use of names 

 have been corrected. 



ACKNOWLEDGMENTS. 



The greater part of the present revision was completed through a 

 study of specimens in the Biological Survey collection, but without 

 the additional material in other museums and private collections the 

 results would have been very imperfect. The friendly assistance and 

 cordial cooperation of the leading museums in the United States and 

 Canada and of private collectors have done much toward making 

 possible the results thus far obtained. 



It is with great pleasure that I acknowledge my mdebtedness to 

 Dr. Joseph GrioneU, director of the Museum of Vertebrate Zoology, 

 University of California; ^Ir. Gerrit S. ^liller, jr., curator of mam- 

 mals, United States National Museum; Dr. J. A. Allen, curator of 

 mammals and birds, American Museum of Natural History; LIr. 

 Charles B. Cory, curator of the Department of Zoology, Field Museum 

 of Natural History; Mr. Samuel Henshaw, curator of mammals, 

 Museum of Comparative Zoology; Dr. Witmer Stone, curator of 

 the Academy of Natural Sciences of Philadelphia; and Prof. J. C. 

 Branner, in charge of the biological collections at Stanford Univer- 

 sity; not only for the use of the large collections under their care, 

 but for courtesies and assistance m working on the collections at these 

 respective museums. For the use of specimens borrowed I am 

 LQdebted to ^Ir. Francis Kermode, curator of the Provincial Museum, 

 Victoria, British Columbia; Mr. P. A. Tavemer, of the Victoria 

 Memorial Museum^ Ottawa, Ontario; Prof. C. D. Bunker, in charge 

 of the collection of the Kansas University Museum; Prof. William B. 

 BeU, of the North Dakota Agricultural College; Dr. B. W. Evermann, 

 director of the Museum of the California Academy of Sciences; 

 Mr. William L. Finley, of the Oregon Fish and Game Commission; and 

 Prof. John F. Bovard, in charge of the University of Oregon Museum. 

 To private collectors my thanks are especially due to ^ir. E. E,. 

 Warren, ]Mr. Stanley G. Jewett, Dr. William Bebb, Mr, W, D. 

 HoUister, and Mr. Ernest Thompson Seton. 



