Female: Six adults from Nebraska yield average and extreme measurements as follows: Total length, 192 (184-225); length of tail, 35 (28-40); length of hind foot, 23 (20.5-26).
_Color._--Winter pelage ordinarily white; as described in _M. r. eskimo_ except possibly paler and certainly with line of demarcation on side of head between upper parts and underparts passing almost straight back without the dorsally directed reëntrant angles of white behind the eye and ear; least width of color of underparts in four specimens from Nebraska averaging 80 (49-89) per cent of greatest width of color of upper parts, but in a fifth animal in summer pelage the brown color of the upper parts encircles the body.
_Skull._--See measurements in table and plate 15; weight 1.1 grams (male from Brown Co., S. D.); basilar length, 30.7 in male from Clay Co., Neb., and 28.8 in female from same county; otherwise as described in _M. e. richardsonii_.
_Remarks._--In his revisionary treatment of the American races of _Mustela rixosa_, Myron H. Swenk (1926:313) credits Samuel Aughey with recording this animal, _M. r. campestris_, from Nebraska, as early as 1880, under the name _Putorius pusillus_. In 1908, Swenk recorded the animal from the same state under the name _rixosus_ and in 1913 the race _campestris_ was formally named by H. H. T. Jackson.
On the testimony of a friend who had previously obtained several specimens for him, Swenk (1926:321) records the least weasel from Oshkosh, Garden County, Nebraska, which is a marginal record of occurrence to the southwest for _M. r. campestris_.
At an early stage in the study of American weasels the writer examined the specimens from Nebraska saved by Mr. Myron H. Swenk and recorded measurements of them. However, at the time of writing this account the specimens were not available for examination and the account of coloration is accordingly incomplete.
The large size, particularly the large external measurements, comprises the principal distinguishing character of this subspecies of the least weasel.
Of the four adults examined from Iowa and South Dakota one exhibits lesions such as result from infestation of the frontal sinuses by nematodes.
_Specimens examined._--Total number, 21 as follows. Arranged alphabetically by states and by counties, from north to south in each state. Unless otherwise indicated, specimens are in the United States National Museum.