_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, Ml #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. _Type._--Female, adult, skull and skin; no. 2490/1886, Amer. Mus. Nat. Hist.; San Francisco Forest [then (1886?), Yavapai County], Arizona; June 20, 1886; obtained by Edgar A. Mearns. The skull (plates 31-33) is complete and unbroken save for a small puncture in the right squamosal. The incisors above and below and M^2 and P^2 on each side are missing. Four canines are preserved separately. Otherwise the teeth are in place. The skin has been taken down from a mount. Some hair has been lost from in front of the ears. Seven mammae are evident and show the animal to have been nursing young. The slightly faded color was mentioned by Mearns in the original description. He says (1891:234): "The memorandum of the colors was made before skinning, the specimen having been subsequently preserved in a solution of alum and salt, which extracted much of the coloring matter." _Range._--Transition to Hudsonian life-zones of Arizona and extreme western New Mexico, along the Colorado River, and south of the Little Colorado River, from San Francisco Mountain region along Mogollon Plateau to extreme western New Mexico. See figure 29 on page 221.