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 ho