Study of the specimens here assigned to _spadix_ reveals that some features regarded as of diagnostic value for one or the other of the two races, _longicauda_ and _noveboracensis_, behave differently. For example, the dark coloration of the upper parts, which is characteristic of _noveboracensis_, manifests itself far westward within the range of _spadix_ whereas the wider extent of the light-colored underparts, which is characteristic of _longicauda_, and the Olive Ocher, rather than Pale Orange Yellow, color of these underparts, are seen in varying degree all the way across the range of _spadix_. Thus, these animals are colored above like _noveboracensis_ and below like _longicauda_, but not _vice versa_. In these animals, then, the _longicauda_ type of underparts is dominant, in one sense of the word, over the _noveboracensis_ type of underparts, and the _noveboracensis_ type of upper parts is dominant over the _longicauda_ type of upper parts. Each of these features is subject to actual intergradation and does not always behave as a "unit character," that is to say, one which is either present or absent. However, the _noveboracensis_ type of upper parts is carried much farther west before being diluted than is the _noveboracensis_ type of underparts. Indeed, within the range of _noveboracensis_ itself, the broad extent of the _longicauda_ type of underparts is manifest. This is, of course, near the western margin of the range of _noveboracensis_. The large size of males of _spadix_, as exemplified by specimens from Elk River (see measurements on p. 421), seems to be retained across the northern part of the range here assigned to the subspecies. This larger size than is found in _longicauda_ from Alberta, is shown also by some specimens from eastern North Dakota which are assigned to _longicauda_. However, the average of these Dakotan specimens, all characters considered, is nearer to my concept of _longicauda_. Inspection of the cranial measurements of _spadix_ shows also that in addition to its large size it is distinguishable from any one of the geographically adjoining races by its relatively (to basilar length) greater, as well as actually greater, mastoidal breadth. This might be included with size as a unique character distinguishing _spadix_ from _longicauda_ and _noveboracensis_. However, it is not clear whether or not this greater mastoidal breadth is more than a function of the large size.