Another female, no. 171559, U. S. Nat. Mus., from Lookout Mountain, 1500 ft., Fort Payne, Alabama, is barely subadult. The external measurements are nearer those of _olivacea_. The color and narrowness of the underparts are typical of _noveboracensis_. The proportions and especially size of the skull show approach to _olivacea_, though they are nearer to _noveboracensis_ when all features are taken into account. In the northern part of its range individuals of _noveboracensis_ attain larger size than farther south. This tendency reaches its extreme, in males at least, in _M. f. occisor_ of Maine. Specimens of _noveboracensis_ from the Adirondacks of New York average larger (see cranial measurements on page 418) than those from farther south, and thus approach _occisor_ in size as well as in geographic position. Also, occasional individuals which strongly show characters of _occisor_ are found even farther south than the Adirondacks of New York. This is true of no. 96518, U. S. Nat. Mus., [M] ad., from Lunenburg; Massachusetts. The animal has a large skull of relatively great width much as in _occisor_, although its external measurements, relative length of tail and long, terminal, black brush place it with _noveboracensis_ rather than with _occisor_. Of a pair of specimens from Ossipee, New Hampshire, the male, no. 77108, U. S. Nat. Mus., has a long (175 mm.) tail, and short (60 mm.) black pencil as in _occisor_, although otherwise it is referable to _noveboracensis_. Still another specimen, a subadult male, no. 4193, Mus. Comp. Zoöl., from Upton, Maine, has a longer (51 mm.) hind foot than _noveboracensis_ although it otherwise agrees with that subspecies. As remarked by Bangs (1899:55), other than fully adult specimens from the range of _occisor_ are "troublesome," and would not be selected as distinct from _noveboracensis_ if placed in a series of that subspecies, say, from New York State. In view of the facts that several specimens from intermediate localities combine the characters of _noveboracensis_ and _occisor_, that _noveboracensis_ in the northern part of its range averages larger than it does farther south and thus approaches _occisor_ in size, and that occasional large specimens resembling _occisor_ in several, but not all, features sometimes crop up in the northern part of the range of _noveboracensis_, it appears that _noveboracensis_ and _occisor_ intergrade. Therefore they are treated as two subspecies of the single species, _Mustela frenata_. Intergradation with _M. f. primulina_ has been commented on in the discussion of that subspecies. Female, no. 159980, U. S. Nat. Mus., from Golconda, Illinois, has many characters of _primulina_ but two young males from there agree better with _noveboracensis_.