_Specimens examined._--Total 7. Fremont Co.: Garden Park, Cañon City, 5344 ft., 1; _2-9/10 mi. E Cañon City, 5344 ft._, 6. SUMMARY A study of 249 specimens of _Thomomys bottae_ from Colorado reveals six subspecies in the state. _T. b. aureus_ and _T. b. howelli_ occupy the Colorado Plateau Region in the western and southwestern parts of the state. _T. b. internatus_, _T. b. cultellus_, _T. b. pervagus_, and the newly named _T. b. rubidus_ occupy part of the Southern Rocky Mountain Region and a narrow strip of the Great Plains. The greatest amount of geographic variation, in _Thomomys bottae_ in Colorado, occurs in the ecotone between the grassland and coniferous forest at the edge of the Great Plains, and in the ecotone between the Piñon, juniper, and sage of the Colorado Plateau and the Coniferous forest of the southern Rocky mountains. TABLE 1. MEASUREMENTS, IN MILLIMETERS, OF THOMOMYS BOTTAE Unless otherwise noted, specimens are adults from Colorado Key to Headings: A: Catalog number or number of individuals averaged B: Total length C: Tail D: Hind foot E: Condylobasal length F: Nasal length G: Zygomatic breadth H: Squamosal breadth I: Length of rostrum J: Breadth of rostrum K: Alveolar length of upper max. tooth-row L: Least interorbital breadth =============================================================== Sex| [A] |[B]|[C]|[D]| [E]| [F]| [G]| [H]| [I]| [J]|[K]|[L] ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | _Thomomys bottae howelli_, holotype ---+---------+---+---+---+----+----+----+----+----+----+---+--- F | 75684[1]| | | | | | | | | | | | sad. |219| 71| 29|37.3|11.1|23.7|20.0|14.5| 8.5|7.7|6.6 | +---+---+---+----+----+----+----+----+----+---+--- | | _Thomomys bottae aureus_, Bedrock | +---+---+---+----+----+----+----+----+----+---+--- F | 2982[2] |217| 59| 31|40.4|13.8|24.3|20.6|16.7| 8.6|9.2|6.8 F | 3013[2] |210| 60| 29|38.7|13.0|24.4|20.4|15.7| 8.1|8.9|7.0 | | | | | | | | | | | | M | 2997[2] |242| 73| 33|44.7|15.4|28.4|22.8|15.7|10.1|9.0|7.2 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | Coventry | +---+---+---+----+----+----+----+----+----+---+--- F | 6 av. |222| 61| 31|39.0|12.1|25.4|20.3|15.2| 7.8|8.2|6.8 | Max. |229| 63| 33|40.0|12.8|25.8|20.6|15.6| 8.2|8.5|7.0 | Min. |217| 58| 30|38.3|11.4|25.0|19.3|14.7| 7.5|8.0|6.6 | | | | | | | | | | | | M | 3 av. |259| 70| 35|46.5|15.0|29.3|22.7|17.8| 9.2|9 5|6.7 | Max. |270| 76| 36|48.3|16.0|31.9|23.7|18.0| 9.3|9.6|6.9 | Min. |250| 65| 35|45.5|14.4|27.6|22.2|17.6| 9.2|8.0|6.4 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | Ashbaugh's Ranch and 15 mi. W Cortez