nition of two subspecies is not indicated.
There is also some variation that is the result of wear and molt and one
of us (Kelson) feels that some of the differences are explainable on
this basis. Accordingly, we prefer to adopt a more conservative
taxonomic arrangement than that of Harris for this group of the Costa
Rican squirrels and arrange _Sciurus variegatoides austini_ Harris,
1933, as a synonym of _Sciurus variegatoides rigidus_ Peters, 1863.

~Thomomys bottae alienus~ Goldman

Six specimens (21249-21253, 212706 BS) from Rice, Arizona, were referred
by Goldman (Proc. Biol. Soc. Washington, 46:76, April 27, 1933) to the
subspecies _Thomomys bottae mutabilis_ Goldman when he proposed that
name as new, but these six specimens were not mentioned by him when he
later named _Thomomys bottae alienus_ (Jour. Washington Acad. Sci.,
28:338, July 15, 1938), to which subspecies the specimens in question
might be expected to belong. Examination of the six specimens reveals
that they are intergrades between _T. b. mutabilis_ and _T. b. alienus_
but that the specimens more closely resemble the latter. More precisely,
slightly larger size of skull, greater ventral inflation of tympanic
bullae, and less depressed occipital region ally the specimens with
_Thomomys bottae alienus_, and we identify them as that subspecies. The
two subspecies concerned are not so distinct as are most subspecies of
_Thomomys bottae_.

~Thomomys bottae aphrastus~ Elliott

Bailey (N. Amer. Fauna, 39:58, November 15, 1915) referred three
specimens from San Antonio, Baja California, to _Thomomys bottae
nigricans_. These specimens have not, to our knowledge, been re-examined
subsequently, although the current taxonomic treatment of the pocket
gophers of Baja California by Huey (Trans. San Diego Soc. Nat. Hist.,
10(4):245-268, 1 map, August 31, 1945) excludes _T. b. nigricans_ from
the area of San Antonio. The pertinent specimens are probably Nos.
10810-10812 in the Chicago Natural History Museum. We have examined the
specimens and, using the comparative materials listed under the account
of _T. b. siccovallis_, find them to be intermediate in most characters
between _T. b. aphrastus_ and _T. b. martirensis_. Because they more
nearly resemble _T. b. aphrastus_ in the weakly-spreading zygomatic
arches, we refer the specimens from San Antonio to that subspecies.

~Thomomys bottae jojobae~ Huey

When Huey (Trans. San Diego Soc. Nat. Hist., 10:256,