A New Subspecies of Microtus montanus from Montana and Comments on Microtus canicaudus Miller

Authors present the identification and formal description of a previously unrecognized subspecies of Microtus montanus from the Flathead and Bitterroot valleys of western Montana, diagnosing it by smaller overall size, cranial proportions, reduced molar series, and notably more inflated tympanic bullae. The paper gives a type locality and detailed measurements for the holotype and series, compares the new subspecies with adjacent forms such as M. m. nanus and M. m. canescens, discusses geographic variation and probable range limits, and provides lists of specimens examined and comparative museum material to support the taxonomic conclusions.