In comparison with _streatori_, skulls of males are of about the same size, _anguinae_ being only 9 per cent heavier. The length of the tooth-rows is ordinarily less than, rather than about equal to, the length of the tympanic bulla; sagittal crest wanting rather than present since in _anguinae_ the temporal muscles meet usually only at the posterior end of the braincase instead of all along the midline on its top; tympanic bullae narrower and more nearly flush with squamosal (less protruded from braincase). Relative to the basilar length, the zygomatic breadth is more, the tympanic bullae are narrower, and the braincase is deeper at the anterior end of the basioccipital. The female is 41 per cent heavier than _streatori_, there being no overlap in most cranial and dental measurements. M1, however, is approximately the same size in each subspecies. The tooth-rows and tympanic bulla are of almost equal length whereas in _streatori_ the length of the tooth-rows is less than that of the bulla.
Differences from _olympica_, in males, are: M1 shorter; all other measurements of teeth and parts of skull averaging larger; skull 20 per cent heavier; tooth-rows averaging shorter than tympanic bulla rather than about the same; relative to basilar length, braincase deeper at anterior end of basioccipital and tooth-rows shorter. The skull of the female is 64 per cent heavier, larger in every measurement taken without overlap; temporal ridges meeting, rather than separated, at lambdoidal crest; length of tooth-rows about equal to, rather than shorter than, tympanic bulla; in relation to basilar length, skull deeper, orbitonasal length more, mastoid and zygomatic breadths more, and tympanic bullae shorter.
_Remarks._--References in the literature to this insular race mostly were under the name _streatori_ until 1932 when in the course of the present study the name _anguinae_ was proposed. A few specimens have been taken by nearly every student of small mammals who has collected on Vancouver Island. Arthur Peake and Herbert Laing have probably collected more specimens than any other two zoölogists.
_M. c. anguinae_ is noteworthy for the slight secondary sexual variation in size; the disparity between the two sexes is less than in any other American subspecies of _erminea_. By linear measurement the body of the female is only 7 per cent shorter than in the male (178 versus 191 mm.). Linear measurements and weights of the skulls of the two sexes are further indicative of this approximation in size. By weight the skull of the female is only a fourth lighter than that of the male, or, stated in another way, the male's skull is only a third heavier (1.2 versus 0.9 grams).