From the range of _M. e. invicta_ in the Rocky Mountains, that of _bangsi_ is separated by the Great Plains from a large part of which region the species is unknown. _M. e. bangsi_ differs from _invicta_ in greater degree of sexual dimorphism in size, and in each sex by larger size, narrower light-colored underparts, and deeper braincase as measured at the anterior margin of the basioccipital. In _bangsi_ the braincase is deeper relative to the length of the skull as well as, of course, actually deeper.
Of the two subspecies whose ranges do meet that of _bangsi_, it more closely resembles _richardsonii_ than _cicognanii_. From _richardsonii_, especially from southeastern populations of the same in which the skull is of the same size as in _bangsi_, the latter differs in longer hind feet. This is an average difference and by one interpretation the animals here referred to _bangsi_ might be lumped with some of the populations from the southeastern part of the range of _richardsonii_ and the whole lot treated as intergrades between _richardsonii_ and _cicognanii_. Nevertheless, the animals here referred to bangsi are not geographically intermediate between _richardsonii_ and _cicognanii_ and this consideration had much to do with the decision to recognize as a separate subspecies the animals here named _bangsi_.
Within the range of the subspecies there is some geographic variation; the hind feet of animals from Iowa average slightly shorter than those of animals from Minnesota and Wisconsin but are nowhere nearly so short as in _cicognanii_ at the same latitude in the eastern United States.
It is noteworthy that the few specimens seen from Isle Royal have the long hind feet of _bangsi_ and not the short hind feet of _cicognanii_ which occurs all along the northern mainland.
Because an oft cited record of occurrence even though erroneous, has a way of being repeated in later works, attention is here called to the alleged occurrence of this ermine in northwestern Ohio at New Bremen. Henninger (1921:239) published the original account of the supposed occurrence but as I pointed out in 1937 (p. 304), the specimen concerned proved upon examination to be a female of _Mustela frenata noveboracensis_. Henninger was misled probably by the short tail; the end of the tail had been lost and healed over before the animal's death. The present study has revealed that _M. erminea_ everywhere east of the Cascade Mountains assumes a white winter coat. Had this been known when Henninger obtained his specimen he probably would not have wrongly identified the animal from New Bremen which was in the brown, winter pelage.