A late Pleistocene/early Holocene faunal assemblage from Kokoweef Cave (San Bernardino County, California) includes a diverse assemblage of gas- tropods, reptiles, birds, and mammals. Chronological control for the site consists of a single radiocarbon date of 9830 ±150 yr. BP taken from charcoal at ap- proximately the vertical mid-point of the stratigraphic excavation. Microtus and Lemmiscus are extralimital and represent the only arvicoline rodents from the locality. We discovered several distinct morphotypes of the ml of Lemmiscus from Kokoweef Cave, one of which is not known from any other populations, living or extinct. The recovery of an ml morphotype with only four closed tri- angles is notable. This morphology is usually found in middle Pleistocene faunas, but is rare in younger localities. The loss of the 4-triangle morphotype of Lem- miscus represents one of the few documented small mammal morphotype 'ex- tinctions' near the end of the Pleistocene in western North America.