From alascensis, salva differs in that males have the preorbital region slightly wider in relation to the length of the tympanic bulla; also the braincase is smaller, actually as well as in comparison with the preorbital part of the skull. The tympanic bullae do not project so far below the squamosals and the braincase itself is shallower, in adults averaging only 11.5 mm. as against 12.5 mm. The overall depth of the braincase, including the tympanic bullae, when divided into the orbitonasal length gives an average of 93 (90-97) per cent whereas in alascensis the figure is only 85 (78-88) per cent. On this basis alone, everyone of the adult skulls of the two races can be distinguished. The females and subadult males show the same tendency to reduction in depth of braincase but not every individual among them can be surely distinguished. By weight the skull of salva of corresponding sex is only about 6 per cent smaller. Comparisons with initis and celenda are made in the accounts of those subspecies.
Remarks.—Most of the specimens seen were collected by Allen E. Hasselborg, resident on Admiralty Island. On the basis of skulls—few skins, and measurements taken in the flesh, are available—salva more closely resembles alascensis than does any other subspecies so far known from southeastern Alaska. The race on Admiralty Island is only slightly differentiated from alascensis of the adjacent mainland.
Specimens examined.—Total number, 26, all from Admiralty Island, Alaska, arranged in general by localities from north to south, and unless otherwise indicated in the Museum of Vertebrate Zoölogy, University of California.
Alaska. Admiralty Island: Hawk Inlet, 2; Seymour Canal, 4; Mole Harbor, 18 (skulls only); Gambier Bay, 1; no locality more definite than Admiralty Island, 4 (1 in U. S. Nat. Mus.).
Mustela erminea initis Hall
Ermine
Mustela erminea initis Hall, Proc. Biol. Soc. Washington, 57:37, June 28, 1944; Hall, Journ. Mamm., 26:180, July 19, 1945.
Type.—Male, adult, skull and skin; no. 289, Mus. Vert. Zoöl.; Saook Bay, Baranof Island, Alaska; October 9, 1907; obtained by A. Hasselborg, original no. 4.
The top of the skull is fractured on the left side from the anterior nares posteriorly through the postorbital process to the posterior root of the zygomatic arch. On the left lower jaw the canine and three incisors are missing; otherwise the teeth all are present and entire.
The skin is in process of molt, approximately nine-tenths of the incoming white pelage being in place. The skin is well made and in a good state of preservation.
Range.—Chichagof and Baranof islands, Alaska. See figures [25], [26] on pages 95, 134.
Characters for ready recognition (only males known).—Differs from M. e. arctica, in that proximal two-thirds of under side of tail colored same as upper parts rather than same as underparts, zygomatic breadth less than distance between last upper molar and jugular foramen; from M. e. salva in that orbitonasal length and mastoid breadth total more than 35 mm., weight of skull and lower jaws more than 2.1 grams; from M. e. alascensis, by total length more than 317, black tip of tail more than 57 per cent of length of tail-vertebrae, interorbital breadth more than 10.3 and equal to, instead of less than, distance between glenoid fossa and posterior border of external auditory meatus; from M. e. celenda by chest white (not mostly covered by brown patch), breadth of rostrum measured across lacrimal processes less than a third of basilar length; from M. e. seclusa in zygomatic breadth more than distance between last upper molar and jugular foramen.
Description.—Size.—Male: The type and an adult topotype measure, respectively, as follows: Total length, 330, 320; length of tail, 95, 95; length of hind foot, 45, 45.
Female: No external measurements available.
Color.—As described in Mustela erminea richardsonii except that least width of color of underparts averages, in two young female topotypes, 50 (49, 50) per cent of greatest width of color of upper parts. Black tip of tail in three young female topotypes averaging 54 (52-55) mm. which is 67 (63-69) per cent of length of tail-vertebrae.
Skull.—Male (illustrated by type and 1 ad. topotype): See measurements and plates [4]-[6]. As described in Mustela erminea richardsonii except that: Weight, 2.3 and 2.5 grams; basilar length, 39.6, and 40.5; interorbital breadth equal to distance between glenoid fossa and posterior border of external auditory meatus.
Female: No adults available.
From salva, initis differs in that skulls of males average larger in every measurement taken, being 41 per cent heavier. Relative to the basilar length, the interorbital and preorbital parts of the skull are larger; the relatively greater interorbital and mastoid breadths are particularly noticeable. Although the depth of the braincase, including the tympanic bullae, is both relatively as well as actually more than in salva, the depth is relatively less than in alascensis which otherwise differs from initis in about the same way that salva differs from initis. Whereas the interorbital breadth in initis is about equal to the distance between the glenoid fossa and the posterior border of the external auditory meatus, the interorbital breadth is uniformly less than this distance in both salva and alascensis. In comparison with seclusa the teeth are of the same size but all measurements of the skull are larger. The skull of initis is 25 per cent heavier. In relation to the basilar length, the interorbital and preorbital parts of the skull are much less in initis. The preorbital and interorbital regions in initis are relatively smaller in comparison also with arctica. The one measurement of interorbital breadth in initis is greater in relation to the basilar length than in kadiacensis but the rostral region, and all that part of the skull anterior to the braincase, is relatively smaller in initis.