From _alascensis_ and _salva_, _seclusa_ differs in larger teeth, shorter skull, much larger preorbital and interorbital regions, actually as well as in relation to basilar length. Excepting the teeth, which are of about the same size, the same general differences obtain in comparison with _initis_ which, however, is 29 per cent heavier.
From _celenda_, _seclusa_ differs in smaller skull in all parts measured, being 22 per cent lighter. The teeth are about the same size. In relation to its length the skull of _seclusa_ is much broader and deeper. From _haidarum_, _seclusa_ differs in: teeth larger; skull shorter and more convex in dorsal outline along median longitudinal axis; in relation to basilar length, skull broader, deeper and braincase relatively shorter.
_Remarks._--The characters shown in the one available skull are far outside the limits of individual variation for other known subspecies. Other specimens are much to be desired to ascertain what the "average" individual is like and to learn the characters of the female.
_Putorius haidarum_ Preble, Proc. Biol. Soc. Washington, 12:169, August 10, 1898.
_Mustela haidarum_, Miller, U. S. Nat. Mus. Bull., 79:97, December 31, 1912.
_Mustela erminea haidarum_, Hall, Proc. Biol. Soc. Washington, 57:38, June 28, 1944; Hall, Journ. Mamm., 26:181, July 19, 1945.
_Type._--Male, adult, skull, skeleton and skin; no. 94430, U. S. Nat. Mus., Biol. Surv. Coll.; Massett, Queen Charlotte Islands, British Columbia; March 17, 1898; obtained by J. H. Keen; original no. 1800x.
The skull is unbroken and complete except for osseous tissue destroyed in the region of each postorbital process; this is the result of infestation of the frontal sinuses by parasites. The skeleton is complete down to the distal ends of the tibiae; the more distal bones are in the skin. The first, right, upper incisor is missing. Otherwise the teeth all are present and entire.
The skin is in the white, winter pelage but the new under fur is visible along the back and on the head although mostly covered with white hair.
_Range._--Queen Charlotte Islands. See figure 25, page 95.
_Characters for ready recognition._--Differs from _M. e. celenda_ in chest white (not mostly covered by brown patch), proximal two-thirds of under side of tail colored like underparts instead of upper parts, in males basilar length less than 38.2; from _M. e. seclusa_, in male, in zygomatic breadth less than distance between last upper molar and jugular foramen; from _M. e. richardsonii_ and _alascensis_, in both sexes, in proximal two-thirds of under side of tail colored like underparts instead of upper parts, interorbital breadth not less than distance from glenoid fossa to posterior margin of external auditory meatus; from _M. e. anguinae_ and _fallenda_, in both sexes, in light-colored underparts more than half the width of dark-colored upper parts, proximal two-thirds of under surface of tail colored like underparts instead of upper parts, interorbital breadth equal to or more than distance between glenoid fossa and posterior margin of external auditory meatus.