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.
One male, no. 8564, Nat. Mus. Canada, from Max Lake, Turtle Mountain, Manitoba, presents puzzling characters. The external measurements of 465, 170, and 57, are in keeping with the great length of the skull which has a basilar length of 48.8. The tooth-rows are 19.3 in length and the mastoid breadth, 25.4. The relative narrowness indicated by the mastoid breadth is maintained throughout the skull. The only other specimens relating to the Turtle Mountains that have been seen are two male, skins without measurements or corresponding skulls, nos. 38902 and 38903, Amer. Mus. Nat. Hist., labeled as from either "Stump Lake or Turtle Mts.," North Dakota. One of these, no. 38902, is much darker than the other. Possibly it is from the Turtle Mountains and the other, lighter-colored one, is from Stump Lake. Study of additional specimens from the Turtle Mountains might show the existence there of a distinct race.
Four specimens, in the collection of Myron Swenk, from Inland, Clay County, Nebraska, are instructive as showing how intergradation occurs between primulina and longicauda. A subadult male, no. 10, is intermediate in external measurements and in color but in each instance is nearer primulina. The same is true of the least width of the color of the underparts. The color of the underparts extends uninterruptedly over the hind legs to the toes as in longicauda, but is absent from the underside of the tail as in primulina. In the skull, the basilar length, breadth of bulla, and size of teeth are nearer longicauda, as are also the ratios to the basilar length of the length of tooth-rows, breadth of the rostrum, length of the tympanic bulla, and depth of the braincase at the anterior margin of the basioccipital. Ratios to the basilar length of the interorbital breadth, mastoid breadth, zygomatic breadth, and depth of the skull at the posterior borders of the upper molars are nearer to those of primulina. The relatively long rostrum, as represented by the orbitonasal length, is nearest to that of spadix. A young, almost subadult, female, no. 7, agrees with primulina in color, color pattern, and length of hind foot. The other external measurements are intermediate, but nearer those of primulina. Size of skull and teeth are as in longicauda. Relative proportions of parts of the skull are not diagnostic in specimens as young as this female. An adult female, skull only, no. 8, agrees with, or approaches nearer to, longicauda in size of skull and teeth and in relative proportion of every part studied. A juvenile, skull only, of questionable sex, no. 9, provides no diagnostic characters. On the basis of color, these specimens from Inland are distinctly nearer primulina. On the basis of cranial characters they are distinctly nearer longicauda. External measurements are intermediate and are a little nearer those of primulina. By placing the most weight on the cranial characters, the animals may be referred to longicauda. The same may be said of 2 skins, one skin with a skull, from Hastings, Nebraska. In each skin the color-pattern is as in primulina; in one the under side of the tail is nevertheless lighter-colored more as in longicauda and the skull, adult male 121651 American Museum of Natural History, approaches nearer to primulina in narrowness but has the large teeth of longicauda.
Intergradation with neomexicana is suggested by one specimen, no. 7936, Univ. Kans., from Thomas County, Kansas, which has well-developed white facial markings.
The specimen, no. 180, Kansas Agric. College, from Glasco, is mounted, of large size, in white winter pelage, and lacks external measurements. On the basis of its obvious large size, and a hind foot measurement of 49 millimeters obtained from the mounted skin, the animal is provisionally referred to longicauda rather than to primulina.
Putorius culbertsoni is a name now credited to Coues (1877:136). Although Coues probably intended only to indicate that Baird wrote this name on the labels of two specimens in the mammal collection of the Smithsonian Institution, Coues gave an "indication" of the application of the name by publishing at the same time the catalogue numbers of specimens whose labels bore the name and thus, in accordance with article 21 of the International Rules of Zoölogical Nomenclature, himself becomes the author of the name. Of the two specimens mentioned by Coues, only the first recorded by him, no. 4320 (with skull no. 37995, U. S. Nat. Mus.), can now be found.