Type.—Male, adult, skull and skin; no. 186451, U. S. Nat. Mus. (formerly 4485/5120, collection of Dr. C. Hart Merriam); Custer, South Dakota; obtained by Vernon Bailey; original no. 90.
The skull is complete and unbroken. The upper incisors are missing. All the other teeth are present although the premolars, and especially the canines, are much worn, possibly as the result of the animal's efforts to free itself from a trap. The skin is fairly well made, in a good state of preservation, and entire.
Range.—Canadian, Transition and Upper Sonoran life-zones of the Black Hills of South Dakota and adjacent semi-bad-land territory of Wyoming and Nebraska southward to Mitchell, Scottsbluff County. See figure [29] on page [221].
Characters for ready recognition.—Differs from M. f. longicauda in smaller size, adult males having a total length of less than 400, hind foot less than 45, basilar length less than 43.5, and in adult females total length less than 375, and basilar length less than 40; from M. f. nevadensis in near Clay Color rather than near (14 n to l) Brussels Brown of upper parts in summer.
Description.—Size.—Male: External measurements of the type specimen are: Total length, 372; length of tail, 137; length of hind foot, 44. Tail is 58 per cent as long as head and body. Length of hind foot more than basal length.
Female: No external measurements for typical adults are available. No. M1 #41 from Mitchell, Scottsbluff Co., Nebraska, an adult female which is an intergrade with the larger M. f. longicauda, measures as follows: Total length, 367; length of tail, 120; length of hind foot, 41.
Externals.—Longest facial vibrissae dark brown or white and extending beyond ear; carpal vibrissae same color as underparts and extending to apical pad of fifth digit; hairiness of foot-soles (in summer pelage) as shown in figure [20].
Color.—Winter pelage unknown; probably white except, of course, tip of tail. Summer pelage as described in Mustela frenata longicauda except that: Least width of color of underparts averaging, in 3 males from Black Hills, 54 (38-62) per cent of greatest width of color of upper parts. Black tip of tail averaging 43 (40-45) mm. long. Thus, averaging approximately same length as hind foot and in type specimen amounting to 33 per cent of length of tail-vertebrae.
Skull and teeth.—Male (based on the type and no. 7440 Amer. Mus. Nat. Hist., from Hill City, S. Dak.): See measurements and plates [18]-[20]. As described in Mustela frenata longicauda except that: Weight, 3.1 (3.0-3.2) grams; basilar length, 41.0 (40.9-41.0); mastoid breadth not less than postpalatal length; breadth of rostrum more than length of P4; anterior margin of tympanic bulla as far posterior to foramen ovale as width of 4 to 5 upper incisors; height of tympanic bulla more or less than distance from its anterior margin to foramen ovale.
Female (based on no. 7441, American Mus. Nat. Hist., from Black Hills, S. Dak.): See measurements and plates [31]-[33]. As described in Mustela frenata longicauda except that: Weight, 2.0 grams; basilar length 37.6. The skull of the female is 35 per cent lighter than the average for the two males.
Comparison with M. f. longicauda and M. f. nevadensis reveals that the tympanic bullae average more nearly flat and that the skull is smaller.
Remarks.—Animals of this subspecies were described and named by Merriam in 1896 as a distinct species on the basis of two or possibly three specimens from the Black Hills of South Dakota and the name seems never to have been applied to specimens from other regions. Vernon Bailey obtained only the one specimen, the type, on his trip in 1888, but two more were obtained for the American Museum of Natural History by Walter Granger in 1894.
Mustela frenata alleni combines the light coloration of M. f. longicauda with the small size of M. f. nevadensis. Indeed, the size may average less than that of nevadensis. M. f. alleni seems to reach its extreme of small size in the Black Hills of South Dakota. Specimens from Mitchell, Scottsbluff County, Nebraska, here referred to alleni are of larger size and in this respect are intermediate between the subspecies alleni and longicauda. Of the two specimens available from Chadron, Nebraska, and here referred to as longicauda, the female, M1 #6, is almost exactly intermediate in size between alleni and longicauda, whereas the male, M1 #11, is as large as the average-sized longicauda.
None of the nine skulls (5 adults) shows malformation resulting from the infestation of the frontal sinuses with parasites.
Specimens examined.—Total number, 10, as follows.
Wyoming. Crook County: Sundance, 1[91].
South Dakota. Pennington County: Hill City, 1[2]; 20 mi. N Elk Mt, 1[91]. County in question: Black Hills, 1[2]. Custer County: Custer, 2 (1[91], 1[2]).
Nebraska. Scottsbluff County: Mitchell, 4[35].
Mustela frenata arizonensis (Mearns)
Long-tailed Weasel
Plates [19], [20], [21], [31], [32] and [33]
Putorius arizonensis Mearns, Bull. Amer. Mus. Nat. Hist., 3:234, June, 1891; Merriam, N. Amer. Fauna, 11:22, fig. 12, June 30, 1896.
Mustela arizonensis, Miller, U. S. Nat. Mus. Bull., 79:99, December 31, 1912.
Mustela frenata arizonensis, Hall, Carnegie Instit. Washington Publ. 473:106, November 20, 1936.