Synaptomys borealis (Richardson, 1828) . Zool. J., 3:517.

TYPE LOCALITY: Canada, District of Mackenzie, Great Bear Lake, Fort Franklin .

DISTRIBUTION: Alaska to N Washington, USA, eastwards across much of interior Canada to Labrador; disjunct range segment from Gaspe Peninsula, Quebec, to C New Hampshire, USA.

SYNONYMS: andersoni, artemisiae, bullatus, chapmani, dalli, innuitus, medioximus, smithi, sphagnicola, truei, wrangeli .

COMMENTS: Subgenus Mictomys . Pleistocene records establish the species in the Great Basin, far to the south of its current range (see Mead et al., 1992).