but six have mammae that are still prominent on the dried skins and may have had litters prior to their capture. Nine females contained embryos, numbering 3 in two specimens, 5 in four specimens, 6 in two specimens, and 7 in one specimen.

Eutamias quadrivittatus hopiensis Merriam.—Four specimens of the Colorado Chipmunk were obtained by D. A. Sutton at locality 2, at 6800, 6900, 7175, and 8050 feet elevation. All are males taken on May 13 and 14, 1949; the specimens bear numbers 5197, 5198, 5199, and 5201 in the collection of the University of Colorado Museum.

Thomomys talpoides fossor J. A. Allen.—The 27 specimens of the Northern Pocket Gopher (59840-59849, 70086-70102) were trapped at localities 3, 6, 7, 10, 11, and 13. The eight skins from locality 7 differ from those from the other localities on the Mesa in being uniformly duller in color dorsally. No significant difference in size or cranial characters was observed. Specimens assigned to T. t. fossor, in the collection of the Museum of Natural History, from other localities in Colorado differ in color from any of the specimens from the Grand Mesa. Until larger numbers of Thomomys talpoides from other localities in Colorado and from the type locality of T. t. fossor, stated to be at Florida, in southern Colorado, have been studied, the specimens from the Grand Mesa seem best referred to T. t. fossor. Three females from localities 7, 10, and 11 contained embryos (2, 4, and 5 in number), and seven other females from localities 6 and 7 show distinct mammae on the dried skins or were recorded by the collectors as lactating.

Castor canadensis concisor Warren and Hall.—Dams constructed by beavers were seen at locality 4 on June 23, 1954. No specimen was taken.

Peromyscus maniculatus rufinus (Merriam).—The 36 specimens of the Deer Mouse (59921-59956) are from seven localities (3, 4, 6, 10, 12, 14, and 15). The mice vary considerably in color; most of them are like mice of the highlands of Colorado and unlike the paler mice inhabiting the lower areas immediately to the west of the Grand Mesa. Young individuals trapped on June 20, 21, and 22 and judged to range from a month through two months in age, and females containing embryos, attest to a somewhat protracted breeding season on the Grand Mesa.

Neotoma cinerea arizonae Merriam.—Two immature Bushy-tailed Wood Rats (60000-60001) were obtained at locality 3 on July 3.

Clethrionomys gapperi galei (Merriam).—The 22 specimens (60005-60025, 70133) of Gapper's Red-backed Vole were taken at localities 6, 7, and 10, and are clearly referable to C. g. galei, rather than to Clethrionomys gapperi gauti to the south, on the basis of generally dark dorsal pelage, indistinctly bordered broad dorsal stripe, and cranial features. C. g. gauti was described by Cockrum and Fitch (1952, Univ. Kansas Publ., Mus. Nat. Hist., 5:289) on the basis of 14 specimens from southern Colorado and northern New Mexico. Twenty-one additional specimens from five miles south and one mile west of Cucharas Camps, Huerfano County, were obtained from the seventh to the fourteenth of July by the field party led by Tordoff after the party left the Grand Mesa. These specimens substantiate the subspecific distinctness of C. g. gauti in that they agree in external and in cranial appearance with the description of typical C. g. gauti, and are distinct in appearance from specimens of C. g. galei from the Grand Mesa and from other localities in northern Colorado. The six specimens from two localities in Colorado available to Cockrum and Fitch exhibited evidence of intergradation at one locality, and atypical smallness at the other locality. A specimen (70134) taken on June 26, 1956, by Phillip M. Youngman on the Black