Thallus: effuse to determinate, continuous to sparingly and irregularly rimose, rarely areolate, with fine fissures, thin, crowded with many small perithecia, prothallus usually not apparent areoles: plane, polygonal, 0.2-0.3 mm wide surface: green or olive-brown to brown, rarely gray, dull or somewhat shiny, smooth to slightly rough anatomy: undifferentiated, filled by algal cells 5-9 µm in diam. Perithecia: half-immersed to almost superficial, dense; exciple: subglobose, 0.15-0.20 mm wide, hyaline, dark only in overmature perithecia, 15-20 µm thick; involucrellum: hemispherical or slightly conical, extending to exciple-base level, lateral 25-50 µm thick, thinner near the apex, at base arching slightly away from the exciple; periphyses 20-25 µm long, thin, simple asci: clavate, 40-55 x 12-18 µm, 8-spored ascospores: hyaline, simple, ellipsoid to ovate, 12-16(-17) x 5-6(-7) µm Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: epilithic, on various rock types in rather shaded and humid situations, mainly montane World distribution: Europe, Newfoundland, and southwestern North America, rather rare Sonoran distribution: Arizona, southern California, and Sonora. Notes: Many small prominent perithecia on a thin thallus, thin involucrella, and rather small ascospores are distinctive for Verrucaria dolosa. The morphologically identical Verrucaria olivacella has noticeably larger spores (16-19 x 6-8 µm). Verrucaria floerkeana, included in V. dolosa by many authors, differs by both larger spores and perithecia.