Distribution of Sabulina basaltica and S. sororia. A–B Reference maps of western North America and Washington State, indicating locations of inset maps C Known locations for Sabulina basaltica (open black circles) within the northeastern Olympic Mountains; gray shading indicates the predicted extent of potential habitat based on exposures of oceanic basalt rocks at subalpine to alpine elevations D Known locations for Sabulina sororia (open black squares) within the Twin Sisters Range; gray shading indicates the predicted extent of potential habitat based on exposures of dunite rock away from large snowfields at subalpine to alpine elevations.