_Characters for ready recognition._--Differs from _M. f. nevadensis_ by presence of light facial markings and Buckthorn Brown rather than near (14_n_ to _l_) Brussels Brown color of upper parts; from _M. f. munda_ by Buckthorn Brown rather than near (_l_) Sudan Brown, or near (_l_) Antique Brown color of upper parts and lesser size, in adult males basilar length less than 45 and hind foot less than 47; from _M. f. nigriauris_ by lighter color in same way as from _munda_ and also by having inside of ears same color as back rather than much darker than back; from _M. f. pulchra_ in hind foot of males less than 46 and narrower skull, in males having breadth of rostrum less than 13.9 and mastoid breadth less than 26.0, see comparison of skulls in the account of _pulchra_. _Description._--_Size._--Male: Three adults, from Fresno, Selma and Los Banos, measure, respectively as follows: Total length, 425, 417, 450; length of tail, 152, 154, 180; length of hind foot,--, 43, 44. Tail averages 61 per cent as long as head and body. Length of hind foot less than basal length. Female: Adults from Selma, Los Banos, and 4 mi. SW Turlock, measure respectively as follows: Total length, 357, 365, 395; length of tail, 133, 132, 145; length of hind foot, 40, 38, 41. Tail averages 58 per cent as long as head and body. Length of hind foot less than basal length. The average differences in external measurements between the two sexes, as represented by these six specimens, are: Total length, 65; length of tail, 25; length of hind foot, 3.5. One adult male weighs 274 grams and 2 adult females 182 and 214 grams. _Externals._--As described in _Mustela frenata nigriauris_.