. Distribution of mammals in Colorado. Mammals. 124 MONOGRAPH MUSEUM OF NATURAL HISTORY NO. 3. Fig. 46. Distribution of Spermophilus tridecem- lineatus in Colorado. 1. S. t. arenicola. 2. S. t. blanca. 3. S. t. pallidus. 4. S. t. parvus. For explana- tion of symbols, see p. 9. Comparisons.—From S. t. pallidus, geo- graphically adjacent to the north, S. *. arenic- ola differs in generally smaller external size, slightly smaller average cranial size, and paler (more reddish) color of dorsal stripes (after A. H. Howell, 1938:111). For comparison with S. t. blanca, see account of that sub- species
. Distribution of mammals in Colorado. Mammals. 124 MONOGRAPH MUSEUM OF NATURAL HISTORY NO. 3. Fig. 46. Distribution of Spermophilus tridecem- lineatus in Colorado. 1. S. t. arenicola. 2. S. t. blanca. 3. S. t. pallidus. 4. S. t. parvus. For explana- tion of symbols, see p. 9. Comparisons.—From S. t. pallidus, geo- graphically adjacent to the north, S. *. arenic- ola differs in generally smaller external size, slightly smaller average cranial size, and paler (more reddish) color of dorsal stripes (after A. H. Howell, 1938:111). For comparison with S. t. blanca, see account of that sub- species. Measurements.—Mean (and extreme) ex- ternal measurements of 12 males, followed by those of four females, all from Baca County, are: (216-251), (225-253); (61-82), (70-82); (30-35), (32- 35). Two males and a female weighed , , and , respectively. For cranial measurements, see table 11. Remarks.—Specimens from montane val- leys of Custer and Huerfano counties are markedly smaller in external and cranial size than specimens of arenicola from the plains of southeastern Colorado. In addition, indi- viduals from the Wet Mountain Valley are much darker in color than is usual in arenic- ola. The incidence of such a pattern of varia- tion in semi-isolated peripheral populations of S. tridecemlineatus is frequent in montane areas of Colorado and adjacent states (see Armstrong, 1971b). Specimens from West- cliff e were referred by A. H. Howell (1938: 119) to the subspecies S. *. parvus, the geo- graphic race of the Wyoming and Uinta ba- sins. Records of occurrence.—Specimens examined, 30, distributed as follows: CHEYENNE COUNTY: Eu- reka Hill, 4850 ft., 1 (USNM). CUSTER COUNTY: 4 mi. W Westcliffe, 1 (CU); Westcliffe, 7800 ft., 2 (WC). KIOWA COUNTY: Eads, 1 (DMNH); no locality other than county, 1 (DMNH). HUERFANO COUNTY: 3 mi. N Muddy Creek, 1 (WC); 1 mi. S, 2 mi. W Walsenburg, 6400 ft., 1 (KU); La Veta, 7012 ft., 1 (KU). BENT COUNT
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