Bole and Moulthrop (1942:165) applied the name _Z. h. hardyi_ (= _acadicus_) to the mice inhabiting a large area from coastal Maine and central New Hampshire through southern New England, New York, northwestern Pennsylvania, and northeastern Ohio. I agree with Bole and Moulthrop (_loc. cit._) that the population of _Zapus hudsonius_ from Maine, New Hampshire, west-central and northern New England are different from neighboring subspecies and are referable to _Z. h. acadicus_, but find that material from extreme southern Massachusetts, Connecticut, southern New York, northwestern Pennsylvania, and northeastern Ohio is best referred to _Zapus hudsonius americanus_ (see account of that subspecies). Intergradation between _Z. h. americanus_ and _Z. h. acadicus_ is indicated by specimens from Berlin, Rensselaer County, New York. In color of ears, length of zygomata, and size and shape of the incisive foramina these specimens are more nearly like _Z. h. americanus_ but in size and shape of the auditory bullae, breadth of the mastoid region, and general appearance of the pelage they are more nearly like _Z. h. acadicus_ and are here referred to _acadicus_. Specimens from Glenville, Schenectady County, New York, are intermediate in cranial characters between _Z. h. americanus_ and _Z. h. acadicus_ but in color are best referred to the latter. Specimens from 1 mi. S Ayer, Worchester County, Massachusetts, are like _Z. h. americanus_ in their short zygomata, narrow mastoid region and suffusion of the underparts; nevertheless, in the shape of the auditory bullae, breadth of the pterygoid fossae, and greater condylobasal length the specimens are more nearly like _Z. h. acadicus_ which they are here considered to be. Animals from Essex and Wilmington, Essex County, Massachusetts, are like _Z. h. americanus_ in external size and in the size and shape of the auditory bullae; but they are more nearly like _Z. h. acadicus_ in most cranial characters and in the general color of the pelage and are here assigned to _Z. h. acadicus_. Specimens from Keene Valley, Essex County, New York, considered by Batchelder (1899:4) to be _Z. h. canadensis_, are in color, length of the zygomata, and size and shape of the auditory bullae more nearly like _Z. h. acadicus_ to which subspecies they are here assigned. A specimen from Orwell, Addison County, Vermont, that Batchelder (_op. cit._:5) referred to _Z. h. canadensis_ is more nearly like _Z. h. acadicus_ in the shape of the auditory bullae, length of the zygomata, and color of the pelage, and is here referred to _Z. h. acadicus_. Specimens from western New Brunswick, referred to _Z. h. canadensis_ by Anderson (1942:37), are more nearly like _Z. h. acadicus_. Specimens from Ste. Anne des Monts, Gaspé Peninsula, Quebec, are intermediate between _Z. h. canadensis_ and _Z. h. acadicus_ in color and size and also in the shape of the auditory bullae but are best referred to _Z. h. acadicus_.