Thallus: irregularly granular-areolate, thin, sometimes becoming subgelatinous when wetted, partly with a dark fimbriate prothallus areoles: convex to flattened, 0.1-0.2 mm thick, dispersed to crowded in scattered patches or coalescing to form an uneven irregularly areolate crust surface: brown to brown-black, dull, rough anatomy: paraplectenchymatous throughout, with a pigmented uppermost cell layer, without an epinecral layer, with mycobiont cells 5-8 µm in diam. and algal cells 6-10 µm in diam. distributed over most of the thallus Perithecia: prominent, hemispherical, inconspicuous as of the same color as thallus; exciple: brown, 0.2-0.3 mm wide, subglobose or depressed-ovate ; involucrellum: hemispherical, with a thin thalline covering, appressed to the exciple, extending down as far as the base of the perithecium, 30-60 µm thick, even in thickness or somewhat broadening or thinning toward base; periphyses 15-25 µm long, rather thickish asci: clavate, 70-80 x 16-22 µm, 8-spored ascospores: hyaline, simple, ellipsoid, 17-22 x 8-10 µm Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: epilithic, on calcareous rocks and caliche World distribution: Europe and North America Sonoran distribution: Arizona, southern California, and Baja California. Notes: Verrucaria fusca resembles V. memnonia but the latter has smaller spores. Verrucaria inornata is also similar but has thinner involucrella, colorless exciples, and larger spores.