Bailey, in his revision of the American voles of the genus _Microtus_ (N. Amer. Fauna, 17:20), showed _Arvicola modesta_ Baird to be a subspecies of _Microtus pennsylvanicus_ but retained _Microtus aztecus_ (Allen) as a distinct species. In describing _M. aztecus_ he wrote "the size similar to _M. pennsylvanicus_, but with shorter tail and larger hindfoot; skull long; braincase narrow; interparietal long ..." and remarked that "_Microtus aztecus_ belongs to the _pennsylvanicus_ group. Externally it is not very different from _modestus_, but none of the specimens show any signs of intergradation; and the skull characters are so well marked that there seems no doubt of its full specific rank." Subsequent to the publication of Allen's (_op. cit._) account and Bailey's account (_op. cit._), additional material was collected that helps to clarify the relationships of _Microtus aztecus_. A comparison of six adult topotypes of _Microtus aztecus_ with a series of nine adults of _M. p. modestus_ from 1 mi. S, 2 mi. E Eagle Nest, 8100 ft., Colfax County, New Mexico, with three adults from 1-1/2 mi. E Manassa, Conejos County, Colorado, and with four adults from Saguache County, Colorado (all in KU), reveals that the supposed "well marked" external and cranial differences between the two forms are not nearly so evident as was indicated by Bailey. The cranial differences that exist between these two forms (narrower nasals, slightly longer interparietal, slightly longer and narrower skull in _aztecus_) are evident only as averages. Although geographically intermediate specimens are lacking, the morphological differences between the two kinds of animals are of the degree and kind that separate subspecies, rather than species. We therefore judge _M. aztecus_ (Allen) to be only subspecifically distinct from _M. pennsylvanicus modestus_ and employ the name _Microtus pennsylvanicus aztecus_. Microtus pennsylvanicus funebris (Dale) 1940. _Microtus pennsylvanicus funebris_ Dale, Jour. Mamm., 21:338, August 14, type from Coldstream, 1450 ft., 3-1/2 mi. SE Vernon, British Columbia. Taylor and Shaw (Occas. Papers Charles R. Conner Mus., State College Washington, 2:24, December, 1929) list under _Microtus nanus_ [= _montanus_] _canescens_ material from Calispell Peak, Washington. Probably the basis for this record is a specimen in the Biological Surveys collection (adult male, 236474) taken on May 9, 1921, by G. G. Cantwell, and labelled as Calispell Peak, 9 mi. W Locke, 3500 ft., Pend Oreille County. An examination (by Hall and Kelson) of the specimen discloses that it is of the species _Microtus pennsylvanicus_, and that it falls within the geographic range ascribed to the subspecies _Microtus pennsylvanicus funebris_ by Dalquest (Univ. Kansas Publ., Mus. Nat. Hist., 2:346, April 9, 1948). Microtus oeconomus amakensis (Murie)