not yet developed mastoidal crests because the animals were not yet adult. Anyone who examines the specimens that Howell used will do well to bear in mind the circumstances noted above concerning Howell's paper of 1906; otherwise the reasons for Howell's identifications of certain specimens can not be understood. We have examined and compared the holotypes, and other specimens used by Howell. While doing so we have borne in mind the degree of individual variation well shown by each of several series of specimens (for example, that in six adult males, from the Animas Mountains of New Mexico, recorded by V. Bailey, N. Amer. Fauna, 53:339, 1932) and age variation (for example, that shown in specimens of _S. interrupta_ from Douglas County, Kansas). The degree of each of these kinds of variation, although considerable, is not extraordinary. That is to say, the variations are of approximately the same degree as we previously have ascertained to exist in _Mephitis mephitis_ and in _Mustela frenata_, two species that are in the same family, Mustelidae, as _Spilogale_. As a result of our comparisons, we conclude, first that the four names mentioned at the beginning of this account all pertain to one species, and second that the three names _S. gracilis_, _S. p. arizonae_ and _S. ambigua_, and probably also _S. leucoparia_, were based on individual variations in one subspecies. _S. gracilis_ has priority and will apply; the other names are properly to be arranged as synonyms of it, as follows: 1890. _Spilogale gracilis_ Merriam, N. Amer. Fauna, 3:83, September 11. 1890. _Spilogale leucoparia_ Merriam, N. Amer. Fauna, 4:11, October 8. 1891. _Spilogale phenax arizonae_ Mearns, Bull. Amer. Mus. Nat. Hist., 3:256, June 5. 1897. _Spilogale ambigua_ Mearns, Preliminary diagnoses of new mammals ... from the Mexican boundary line, p. 3, January 12.