Compared with the skull of the male of _nevadensis_ that of _munda_ averages larger in every part measured and specimens from Point Arena are nearly as heavy again, have relatively more expanded zygomata and mastoid processes but are relatively narrower anteriorly as shown by the breadth of the rostrum, interorbital breadth and postorbital breadth. Also the braincase is less inflated anteriorly, the tympanic bullae are lower and the skull is more angular. Females show the same differences although in different degree. Compared with the skull of the male of _M. f. nigriauris_, that of _munda_ from Point Arena averages larger in every part measured except for the length of the upper tooth-rows. Relative to the basilar length, the skull of _munda_ averages broader across the mastoids and across the zygomata, is deeper through the braincase at the anterior end of the basioccipital, and has a greater development of the lambdoidal crest. _Remarks._--The skin and part skull, no. 536/1849, U. S. Nat. Mus., taken by Lieutenant W. P. Trowbridge at San Pablo Bay, is the first specimen known to have been saved of this subspecies. Since 1899 when O. Bangs diagnosed _munda_ as of small size, the weasel of the humid costal belt north of San Francisco Bay has been regarded as smaller than bridled weasels from farther south in the State. Actually, however, the weasel of the humid costal belt shares with _M. f. pulchra_ the distinction of being one of the two largest weasels in California. _M. f. munda_ may be a composite subspecies, for the variation in facial markings, in coloration otherwise, in external measurements and in size and shape of skull is great. At one time in the course of the present study, manuscript accounts of two subspecies were prepared for the animals now all called _munda_ and there is still much justification for recognizing two subspecies, one, along the coast proper, the larger, darker-colored animal with reduced white facial markings and large, wide, heavily ridged skull from Point Arena, and 6 miles south of Laytonville, Mendocino County, along with the specimens from 5 and 6 miles west of Inverness, Marin County, and the other, an inland race, which is a smaller, lighter-colored animal with more extensive white facial markings and a smaller, narrower, skull, known by specimens from Point Reyes [station?], Nicasio, 15 mi. north of San Rafael, Freestone, Vallejo, and Mount Sanhedrin. The differences between these two lots of specimens are of great degree. However, a female from Fort Bragg proves to be no larger than three females labeled as from Point Reyes. Also, a male from 2 miles south and one mile east of Stewarts Point on the coast has a skull no larger than the animal from Vallejo, whereas the skin alone of an adult female from 3 miles south of Stewarts Point is large and agrees with the specimens from Point Arena. Consequently, no logical ranges can be worked out for the two variants with the material now available.