The facts are that a critical taxonomic study of the American specimens of the subgenus _Stenocranius_ is required in order to ascertain the geographic variation. One of us (Hall) has examined the holotypes of the kinds named from Alaska, and the material listed by R. Baker (Univ. Kansas Publ. Mus. Nat. Hist., 5:109) of the two kinds named from Canada. The degree and nature of the variation shown by these specimens lead us to the conclusion that all are of a single species. If the American mouse is specifically distinct from any of the previously named Asiatic species--at this writing we lack material to decide this question--the named kinds from the mainland of the New World may stand as follows: MICROTUS MIURUS ANDERSONI Rand. 1945. _Microtus andersoni_ Rand, Bull. Nat. Mus. Canada, 99:42, prior to June 20, type from near headwaters of Little Keel River, 5500 ft., 82 mi. W Mackenzie River on Canol Road, Mackenzie. MICROTUS MIURUS CANTATOR Anderson. 1947. _Microtus cantator_ Anderson, Bull. Nat. Mus. Canada, 102:161, January 24, type from mountain top near Tepee Lake, 61° 35' N, 140° 22' W, N slope Elias Range, Yukon Terr. MICROTUS MIURUS MIURUS Osgood. 1901. _Microtus miurus_ Osgood, N. Amer. Fauna, 21:64, September 26, type from head of Bear Creek, in mts. near Hope City, Turnagain Arm, Cook Inlet, Alaska. MICROTUS MIURUS MURIEI Nelson. 1931. _Microtus muriei_ Nelson, Jour. Mamm., 12:311, August 24, type from Kutuk River (tributary of Alatna River), Endicott Mts., Alaska. 1950. _Microtus miurus paneaki_ Rausch, Jour. Washington Acad. Sci., 40:135, April 21, type from Tolugak Lake (lat. 68° 24' N, long. 152° 10'), Brooks Range, Alaska. MICROTUS MIURUS OREAS Osgood. 1907. _Microtus miurus oreas_ Osgood, Proc. Biol. Soc. Washington, 20:61, April 18, type from Toklat River, Alaskan Range, Alaska. _Transmitted July 8, 1952._