Specimens to the number of 1,045 have been available for this study. Whereas Bailey (loc. cit.) listed only four kinds belonging to four different species, thirty-five kinds are now known from Utah. Seven of these are herein described as new. The thirty-five kinds are found to belong to only two instead of four full species.

Inasmuch as the literature is scattered and since names have been applied in different ways at different times, I have attempted to give a synonomy as complete as possible for each form found within the state.

The bibliographies of Hayward (1936 and 1941) and Miller's (1924) "List of North American mammals" have been of great use.

Capitalized color terms in the accounts are after Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912.

In the lists of specimens examined, the localities are listed by counties from west to east, beginning at the northwestern corner of the state, and within each county from north to south. When two localities are on the same latitude, the westernmost is listed first.

I am deeply indebted to Professor R. V. Chamberlin, of the University of Utah, for encouragement and support in my investigation. I also acknowledge critical assistance in the preparation of this paper from Professor E. Raymond Hall of the University of Kansas. For the loan of specimens I am grateful to the following: Clinton G. Abbott and Lawrence M. Huey, Natural History Museum of San Diego, San Diego, California; Harold E. Anthony and J. Eric Hill, American Museum of Natural History, New York City, New York; Seth B. Benson, Museum of Vertebrate Zoölogy, University of California, Berkeley, California; William H. Burt, Museum of Zoölogy, University of Michigan, Ann Arbor, Michigan; J. Kenneth Doutt, Carnegie Museum, Pittsburgh, Pennsylvania; Ross Hardy, Dixie Junior College, St. George, Utah; C. Lynn Hayward and Vasco M. Tanner, Brigham Young University, Provo, Utah; H. H. T. Jackson and Viola S. Schantz, United States Fish and Wildlife Service, U. S. National Museum, Washington, D. C.; Remington Kellogg and Alexander Wetmore, U. S. National Museum, Washington, D. C.; J. S. Stanford, Utah State Agricultural College, Logan, Utah.

Unless otherwise indicated, specimens are in the Museum of Zoölogy, University of Utah, Salt Lake City, Utah. In lists of specimens examined, abbreviations are employed as follows:

(A. M. N. H.)American Museum of Natural History.
(N. H. M. S. D.)Natural History Museum of San Diego.
(M. V. Z.)Museum of Vertebrate Zoölogy, University of California.
(U. M.)Museum of Zoölogy, University of Michigan.
(C. M.)Carnegie Museum.
(R. H.)Collection of Ross Hardy.
(B. Y. U.)Brigham Young University.
(U. S. N. M.)United States National Museum.
(U. S. A. C.)Utah State Agricultural College.
(K. U.)Museum of Natural History, University of Kansas.