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
In his discussion of the pocket gophers of Baja California, Huey (Trans. San Diego Soc. Nat. Hist., 10:245-268, map, August 31, 1945) made no mention of specimens from Ensenada, Baja California, recorded by Bailey (N. Amer. Fauna, 39:58, November 15, 1915) as Thomomys bottae nigricans. We have examined the specimens from Ensenada available to Bailey in the U. S. Biological Surveys Collection, Nos. 137724, 139890, and 139891, subadult, immature, and adult, respectively. As compared with Thomomys bottae sanctidiegi from the mouth of the Tiajuana River (No. 126028) and T. b. nigricans (topotypes), the one adult specimen from Ensenada agrees with T. b. sanctidiegi and differs from T. b. nigricans in lighter color, larger and more angular skull, and more inflated braincase. The specimens from Ensenada differ from the adjacent subspecies to the south, Thomomys bottae proximarinus [to judge from Huey's (op. cit.) characterization of that subspecies] in lighter color, and larger, more robust skull. Accordingly, the specimens from Ensenada are referred to Thomomys bottae sanctidiegi.
Thomomys bottae siccovallis Huey
Bailey (N. Amer. Fauna, 39:58, November 15, 1915) listed a specimen from Mattomi, Baja California, as Thomomys bottae nigricans. When Huey (Trans. San Diego Soc. Nat. Hist., 10:259, August 31, 1945) revived the name Thomomys [bottae] aphrastus Elliot, and named (op. cit.:258) Thomomys bottae siccovallis he made no mention of the specimen, from Mattomi, which, on geographic grounds, would be expected to be T. b. aphrastus, T. b. martirensis J. A. Allen, or T. b. siccovallis. We have examined an adult male (10832 CNHM), probably the specimen seen by Bailey (loc. cit.), from Mattomi, and have compared No. 10832 with six topotypes (10813-10816, 10819 and 10820 CNHM) of T. b. martirensis, the type and one topotype (10798 CNHM) of T. b. aphrastus and with the original description of T. b. siccovallis. The specimen from Mattomi seems to be unique in the large size of the tympanic bullae. The specimen in question differs from T. b. martirensis also in shorter and wider skull, shorter and wider rostrum, and longer and wider molariform teeth. In these features resemblance is shown to the holotype of T. b. aphrastus and even greater resemblance is shown to T. b. siccovallis to which the specimen from Mattomi is referred.
Thomomys monticola mazama Merriam
This subspecies of the Cascades of Oregon and Thomomys monticola nasicus of the territory immediately to the east of the Cascades, in the same state, were originally described (Merriam, Proc. Biol. Soc. Washington, 11:214 and 216, respectively, July 15, 1897) and redescribed (Bailey, N. Amer. Fauna, 39:123 and 125, respectively, November 15, 1915) as distinguished from each other by paler color, smaller tympanic bullae and longer nasals in T. m. nasicus. The holotypes do differ in these respects. The assigned (by Bailey, loc. cit.) specimens indicate that the opposite condition obtains with respect to the size of bullae; that is to say, the bullae are smaller in T. m. mazama. In these referred specimens from Oregon the nasals are actually and relatively longer in T. m. nasicus, which averages paler (less black and more red). Certain specimens of the two subspecies that are comparable as to sex, age and season, are indistinguishable in color.
This is the background against which Bailey (op. cit.:125), contrary to his statement of geographic ranges (op. cit.:123, 125) and map (op. cit.:fig. 5, p. 23), assigned, in his list of specimens examined, two specimens ([** Male] ad. 79817 and [** Female] ad. 79818 BS) from Pengra, west of the Cascades, to the subspecies T. m. nasicus. In the specimens from Pengra the bullae are angular as in referred specimens of nasicus (unlike those of the holotype), the rostra are intermediate in length between those of the two subspecies concerned, and the color is light as in T. m. nasicus but can be matched by that of certain specimens of T. m. mazama, for example by that of No. 79821 BS from Diamond Lake, Oregon. Consequently, on morphological grounds, the two specimens from Pengra can be assigned to T. m. mazama almost as well as to T. m. nasicus. Having regard for the geographic relations, we assign them to T. m. mazama.
In making this tentative identification we are aware that the acquisition of more nearly adequate material from Oregon, and critical study of such material, may bring a subspecific arrangement of the populations of Thomomys monticola different from the current one.
Thomomys talpoides bullatus Bailey