_Remarks._--Intergradation with _Zapus hudsonius acadicus_ occurs in southeastern New York as indicated by a series of 25 specimens from Peterboro. They resemble _Z. h. acadicus_ in width of the mastoid region and relatively longer tooth-row, but in the size and shape of the auditory bullae, width of the pterygoid fossae, and lighter, brighter, color of the sides they are more nearly like _Z. h. americanus_ to which they are here referred. Intergradation between _Z. h. americanus_ and _Z. h. acadicus_ is indicated also by specimens from Lawyersville and Schoharie, New York. In animals from both localities the length of the zygomata and the breadth of the mastoid region are more nearly as in _Z. h. acadicus_, but in size and shape of the auditory bullae, over-all length of the skull, color of the ears, and general color of the pelage they are more nearly like _Z. h. americanus_ to which they are here referred. Specimens from western Pennsylvania, judged to be _Z. h. hudsonius_ by Preble (1899:17), and those from northwestern Pennsylvania and northeastern Ohio, allocated to _Z. h. hardyi_ (= _acadicus_) by Bole and Moulthrop (1942:165), are more nearly like _Z. h. americanus_ in size and shape of the auditory bullae, short zygomata, relatively narrow mastoid region, and color of pelage. Specimens from the lower peninsula of Michigan, northeastern Indiana, and northwestern Ohio, described by Bole and Moulthrop (_op. cit._:168) as belonging to a new subspecies (_Zapus hudsonius brevipes_), are to me indistinguishable from most specimens of _Z. h. americanus_. The characters which Bole and Moulthrop (_loc. cit._) ascribe to _Z. h. brevipes_--color bright Ochraceous-Buff, tail and hind feet short, and skull narrow--are also those of _Z. h. americanus_. Specimens from various localities in southeastern Ohio, all within the range ascribed by Bole and Moulthrop (_op. cit._:169) to _Zapus hudsonius rafinesquei_, are indistinguishable from specimens of _Z. h. americanus_ from eastern Tennessee, West Virginia, North Carolina, and Maryland. _Zapus hudsonius rafinesquei_ (at least that part from southeastern Ohio) is indistinguishable from _Z. h. americanus_ and therefore is synonymized under _Z. h. americanus_. Specimens from Lagrange County, Indiana, show intergradation between _Zapus hudsonius intermedius_ and _Z. h. americanus_ in the color of the pelage but are more nearly like _Z. h. americanus_ to which they are here referred. One from Porter County, Indiana, is more nearly like _Z. h. intermedius_ in size and shape of the bullae and in breadth of the pterygoid fossae but in color and degree of lateral bowing of the zygomata is better placed with _Z. h. americanus_.