The skull of the male of _saturata_, relative to the basilar length, is broader across the mastoids and narrower across the rostrum and interorbital region than that of _nevadensis_. Skull not known certainly to differ from that of _oregonensis_. Compared with the skull of _munda_, that of the male of _saturata_ is smaller in every part measured except depth of tympanic bullae which averages 3.6 millimeters, rather than 3.5 as in _munda_. Also, the skull of _saturata_ has a less-marked postorbital constriction, is less heavily ridged, less angular, does not have the impressions of the temporal muscles carried so far forward on the frontal bones and is relatively much narrower across the zygomatic arches. _Remarks._--In 1896, Merriam named _M. f. saturata_ as a distinct species on the basis of one specimen, taken by Clark P. Streator at Siskiyou, Oregon, and a second specimen taken the year previously by Allan C. Brooks at Chilliwack, British Columbia. On the basis of these two specimens, Merriam (1896:22) ascribed to the race a range ". . . on the Cascade and Siskiyou mountains of Oregon and Washington, reaching a short distance into British Columbia." Since that time, this name, _saturata_, has been employed for the dark-colored weasels, of the coastal region of Oregon, Washington, and extreme southwestern British Columbia, which here are arranged under the name _M. f. altifrontalis_. _M. f. saturata_ proves to be restricted to the humid mountainous region inland from the coast in northern California and in the Siskiyou Mountains of southern Oregon. Its range is separated by that of _M. f. oregonensis_ from the range of the darker-colored, deeper-skulled, _M. f. altifrontalis_ of the humid costal region proper.