Type.—Male, adult, skull and skin; no. 74423, U. S. Nat. Mus., Biol. Surv. Coll.; Juneau, Alaska; August 22, 1895; obtained by Clark P. Streator, original no. 4806.
The skull shows malformation of the frontal sinuses due to parasites and lacks osseous tissue where the parasitic infestation was localized. The left exoccipital condyle and adjacent region is less developed than the right and the posterior part of the skull is bent slightly to the left. Otherwise the skull is unbroken. The teeth all are present and entire. The skin is in the brown summer coat, fairly well made and in a good state of preservation. A few white hairs persist where the proximal line of the black hair of the tip of the tail meets the distal line of the brown hair.
Range.—Mainland of southeastern Alaska from Lynn Canal south to include Mitkof, Zarembo, Wrangel and Revillagigedo islands. See figures [25], [26] on pages 95 and 134.
Characters for ready recognition.—Differs from M. e. arctica and haidarum, in both sexes, by proximal two-thirds of under side of tail colored same as upper parts rather than same as underparts and interorbital breadth less, instead of more, than distance between glenoid fossa and posterior border of external auditory meatus; from M. e. salva, in males, by overall depth of braincase including tympanic bullae less than 89 per cent of orbitonasal length, females not individually distinguishable but averaging shallower through the braincase; from M. e. initis, celenda and seclusa by interorbital breadth less than distance between glenoid fossa and posterior border of external auditory meatus (females of initis, celenda and seclusa unknown); further from initis by total length less than 317 and black tip of tail less than 57 per cent of length of tail-vertebrae; further from celenda by chest white, not mostly covered by brown patch.
Description.—Size.—Male: Eight adults from Windham, Alaska, yield average and extreme measurements as follows: Total length, 298 (288-315); length of tail, 88 (84-94); length of hind foot, 41.3 (37-44).
Female: Two adults from Juneau and Helm Bay measure, respectively, as follows: Total length, 258, 258; length of tail,——, 76; length of hind foot, 32, 34.
Color.—As described in Mustela erminea richardsonii except that least width of color of underparts averaging, in five females, 42 (35-53) per cent of greatest width of color of upper parts. Black tip of tail in same specimens averaging 36 (30-40) mm. which is 49 (48-53) per cent of length of tail-vertebrae.
Skull.—Male (based on 8 adults from Windham): See measurements and plates, 2-4. As described in Mustela erminea richardsonii except that: Weight, 1.8 (1.5-2.6) grams; basilar length, 37.5 (36.5-38.9); length of tooth-rows more or less than (about same as) length of tympanic bulla.
Female (based on 5 adults, from localities listed in the table of cranial measurements): See measurements and plates [9]-[11]. As described in Mustela erminea richardsonii except that: Weight, 0.96 (0.7-1.1) grams; basilar length, 32.7 (31.9-33.2); breadth of rostrum more or less than (about equal to) 30 per cent of basilar length.
From richardsonii, alascensis differs in that the skull of the male averages smaller in every measurement taken and is 28 per cent lighter. Relative to the basilar length, the orbitonasal length is more and the braincase is shallower as measured at the anterior end of the basioccipital. The four adult females seen of alascensis are more variable than those of richardsonii and average smaller in some measurements and larger in others but give no proof of any consistent difference.
From haidarum, alascensis differs in that the rostrum and entire preorbital part of the skull is actually as well as relatively much smaller in both sexes. In males of alascensis the length of the skull, and other cranial measurements of length, is more. In males, the mastoid breadth and zygomatic breadth are about the same as in haidarum, as also is the weight. M1 is larger but m1 and P4 are smaller. In females the anteroposterior extent of the inner moiety of M1 and length of tympanic bulla are about the same in the two subspecies but all other cranial and dental measurements in alascensis are less. It is 29 per cent lighter. The difference in the preorbital region is of about the same degree as in the males.
Comparisons of the skull with those of arctica, salva, initis, celenda, and seclusa are made in the accounts of those subspecies.
Remarks.—The relatively few specimens known of this race seem always to have been referred to in the literature by the name alascensis and the nomenclatural history is therefore simple. The original materials were obtained by the collector Clark P. Streator and the additional series of skeletons, one with skin, from Windham were procured by Stanton Price, a resident there.
The subspecies is well differentiated from both arctica and richardsonii. Although actual intergrades are lacking between alascensis and the two races just mentioned I have no doubt that intergradation occurs with richardsonii and think it probably does also with arctica.
The assignment of the three females from Mitkof Island, Zarembo Island, and Loring on Revillagigedo Island, is tentative because each is so young as not to show diagnostic cranial characters. The two other specimens from Revillagigedo Island (Carroll Inlet), labeled as males, are in white winter pelage. Only one, no. 136358, a subadult, is accompanied by a skull. The small size of each specimen, and its cranial characters which are intermediate between those of males and females of alascensis of the adjacent mainland, indicate the existence of a distinct race of weasel on Revillagigedo Island. On the chance that the one specimen with a skull is a dwarf, or is wrongly sexed as seems improbable, the population is tentatively referred to alascensis.