When Goldman (Jour. Washington Acad. Sci., 26:113, March 15, 1936) named the subspecies _Thomomys bottae desitus_, he assigned to it (_op. cit._:114) 10 specimens obtained at Wickenburg, Maricopa County, Arizona. He did not mention specimens from Wickenburg when he subsequently named the subspecies _Thomomys bottae patulus_ (Jour. Washington Acad. Sci., 28:341, July 15, 1938) and stated that _T. b. patulus_ was known only from the type locality in the "bottomland along [the] Hassayampa River, two miles below Wickenburg." Examination in 1950 of specimens referable to _T. b. patulus_ in the U. S. Biological Surveys Collection shows all of them, including the holotype, to be labeled "Wickenburg." The 10 specimens from Wickenburg reported by Goldman in 1936 as _T. b. desitus_ were included by him among the 16 (actually 17, one being a skull only) upon which he based his description of _T. b. patulus_ in 1938. Examination of the field catalogues of 3 of the 4 collectors who obtained the specimens discloses that only the 7 specimens obtained last were recorded as occurring in the Hassayampa River bottoms; the first 10 were recorded only as from "Wickenburg." Briefly, only one subspecies, _T. b. patulus_, is present in the area, and Goldman in 1938 seems to have thought that the two localities were actually the same, and that "2 miles below Wickenburg" was the more precise designation. ~Thomomys bottae providentialis~ Grinnell We have examined a specimen, No. 26120/33526, from 12-Mile Spring, California, in the U. S. Biological Surveys Collection, which Bailey (N. Amer. Fauna, 39:73, November 15, 1945) referred to the subspecies _Thomomys perpallidus_ [= _aureus_] _perpes_. We find the specimen to be referable to the later named _Thomomys bottae providentialis_ on the basis of smaller ear, more massive, more ridged and angular skull, greater interorbital breadth, deeper and thicker rostrum, less globular bullae, and U-shaped rather than V-shaped interpterygoid space. Therefore, 12-Mile Spring is the northernmost locality of occurrence of the subspecies _T. b. providentialis_. ~Thomomys bottae sanctidiegi~ Huey