n Coloradan specimens seems to be the
principal basis for recognizing _Spilogale gracilis tenuis_ A. H.
Howell. Both _S. g. saxatilis_ and _S. g. tenuis_ are "poorly"
differentiated from _S. g. gracilis_ and from each other.

The holotype of _Spilogale ambigua_ Mearns is slightly smaller than
other adult males of comparable age, and the braincase, relative to
its width, is slightly deeper than in the average adult male. These
variations, nevertheless, are within the range of individual
variation, as also are those characterizing the holotype of _Spilogale
phenax arizonae_ Mearns. The latter specimen is an adult male, with
much inflated mastoidal bullae, nearly straight dorsal profile on the
skull, relatively shallow braincase, and only slightly worn teeth.

The holotype of _Spilogale leucoparia_ Merriam, as pointed out above,
is an extreme example of the extensiveness of the white areas of the
pelage at the expense of the black areas. This feature occurs more
often in the southwestern desert areas of the United States than it
does farther north. In addition to the extensiveness of the white
markings, the other two characters allegedly distinctive of _S.
leucoparia_ are broad and much flattened braincase and great degree of
inflation of the mastoidal bullae. Although these three mentioned
features do distinguish _S. leucoparia_ from _S. indianola_ to the
eastward, they seem not to set _S. leucoparia_ apart from _S.
gracilis_ to the westward. For example, in Arizona some specimens are
extensively white and some others have the braincase flattened and the
mastoidal bullae much inflated. V. Bailey (N. Amer. Fauna, 53:339,
1932) refers to a specimen ([Male], No. 147252 USBS) from the head of
the Rio Mimbres in New Mexico in which, as our comparisons show, the
inflation of the mastoidal bullae exceeds that of any Texan specimen
of _S. leucoparia_, the holotype included. Also, at the type locality
of _S. leucoparia_, subadult male No. 188467 USNM and adult male No.
188468 USNM are narrower across the mastoidal region than is the
holotype. In summary and review, specimens from the eastern part of
the range heretofore ascribed to _S. leucoparia_ nearly all have much
inflated mastoidal bullae whereas less than half of the specimens of
_Spilogale_ from western New Mexico and Arizona have these bullae as
greatly inflated; but, in No. 147252 from the head of the Rio Mimbres
of New Mexico the inflation of the bullae is more extreme