Not only is there a difference in length between the skulls of the two extremes of the females but this difference extends to all other dimensions of their skulls, and is most pronounced in the preorbital region. The differences in breadth of the braincase and other parts of the skull are relatively less than the differences in length. Differences of the same nature, although of lesser degree than found in the females, are to be seen in two males. The skull of an adult no. 51590, Mus. Vert. Zoöl., from 6 miles south of Medford, has a basilar length of 46.4, upper tooth-rows, 17.6 mm. long, and a weight of 4.0 grams, whereas corresponding figures for the subadult type specimen from Grants Pass, are only 43.0, 16.2, and 3.3. The wide range of variation in size of skull of both sexes, together with the considerable variation in color pattern of the specimens here referred to _oregonensis_ raises the suspicion that we are using the name in a composite sense; nevertheless, to recognize more than one subspecies with the material now available would be unwise. A subadult female, of abnormal color, no. 47149, Mus. Vert. Zoöl., taken by Mr. H. E. Wilder at Carlotta, California, on December 20, 1930, in a region where weasels do not turn white in winter, is white, except for the black tip of the tail, but has a suffusion of orange. This specimen, discussed at greater length on page 43, is instructive in that it suggests that there are separate determiners for the brown and red elements of the pelage. It is interesting also as suggesting how natural selection may tend to eliminate from the population a conspicuous color-variation of this kind. At any rate, Mr. Wilder (Ms.) states: "This specimen was picked up in a field, where it evidently had been dropped by a hawk or an owl." The braincase of the skull is crushed in three places as though by a raptor's beak. None of the several other weasels, all normally colored, saved by Mr. Wilder from this general locality gives evidence of having fallen a victim to a raptor. Only 2 skulls of the 12 adults and subadults examined show malformation of the frontal sinuses such as results from the presence of parasites. _Specimens examined._--Total number, 29, arranged within states from north to south by counties. Unless otherwise indicated specimens are in the collection of the United States National Museum. =California.= _Del Norte County_: Requa, 1[8]. _Humholdt County_: Eureka, 2 (1[74], 1[75]); Ferndale, 1[74]; Fortuna, 2[63]; Carlotta, 6 (3[74], 3[59]); 12 mi. E Bridgeville, 1[59]; 2 mi. W Bridgeville, 1[59].