_Remarks._--Richardson's (1829:47) account on which Bonaparte may be said to have based his name, records measurements in inches and lines which I transpose into millimeters as follows: Total length, 440 mm.; length of head and body, 305; length of tail (vertebrae), 135; length of tail (including fur), 164 mm. Specimen no. 43.3.3.3 in the British Museum, which has by some persons been regarded as the type, yields measurements as follows: Total length, 408 (which allows for 15 mm. loss of the fleshy part of the end of the tail); length of head and body, 272; length of tail (vertebrae), 136 (= 121 + 15); length of tail (including fur), 162 (142 + 20 mm. that appears to have been lost). Richardson's specimen would appear to have been of unusual proportions and to have been larger than no. 43.3.3.3. Some reasons for and reasons against regarding this specimen as the holotype are given in the account of _M. erminea cicognanii_. The name _longicauda_ was applied to practically all long-tailed weasels of the western United States at one time but as one after another of the geographic variants in the mountainous regions were designated as separable, the name _longicauda_ came to be restricted to the light-colored, relatively large, animal of the Great Plains. The intergradation of _longicauda_ with _spadix_ and _oribasus_ has been commented on in the discussions of those subspecies. The larger size and darker color of specimens referred to _longicauda_ from Devils Lake and Grafton, North Dakota, are features indicative of intergradation there with _spadix_. Two young females from Waterton Lake Park, Alberta, by their darker than average color, suggest intergradation with _oribasus_, as, for that matter, does the specimen from Waterton Lake [= Chief Mountain Lake, in Montana] itself, which, however, is even darker than the two specimens taken on the Canadian side of the line and hence is referred to _oribasus_. An adult female, no. 175586, U. S. Nat. Mus., from Moose Pass, Alberta, examined after the above was written, is larger than any other female seen of _longicauda_ and in this respect may show approach to _oribasus_, which in the northern part of its range is of large size as judged by males from the Bowron Lake region.