Lake Fingernailclam (Musculium lacustre) is a small (shell length up to 5 mm) Holarctic freshwater peaclam. The southernmost occurrence of this species is in New Mexico in upper Cieneguilla Creek in Colfax County. In New Mexico they are found at a high elevation (2,600-2,630 m) in a marshy area with wide seasonal variation in flow, though elsewhere in North America they occur in a variety of habitats.