Life habit: lichenicolous on Staurothele sp. Thallus: areolate, fissured, 0.25-0.60 mm thick, without a visible prothallus areoles: angular in outline (central areoles) to somewhat rounded (marginal ones), slightly convex, 0.5-1 mm wide, basally somewhat constricted to form a stipe-like attachment organ fixing the thallus units within the substrate and leaving a cavity when the areole is removed or falls out surface: whitish gray, dull, minutely wrinkled, roughly pruinose anatomy: upper cortex paraplectenchymatous, 10-20 µm thick, composed of small roundish angular cells (5-6 µm in diam.), overlain by an irregular amorphous epinecral layer up to 20 µm, with cortical paraplectenchyma continuing laterally down the sidewalls of the areoles; algal layer: subparaplectenchymatous, 150-500 µm thick, diffracted by vertically orientated hyphae, with densely packed algal cells 5-10 µm in diam.; alga-free medulla: subparaplectenchymatous, with more numerous interhyphal spaces than in the algal layer, the lower part ±brown and inspersed with fine granules or crystals, merging into the stipe-like attachment organ Perithecia: immersed within the areolae, one to several per areole, entirely sunken into the areoles or with slightly protruding tips; exciple: subglobose, 0.3-0.4 mm broad, hyaline except around the ostiole; involucrellum: lacking; periphyses c. 25 µm long, 3 µm thick asci: clavate, 60-70 x 25 µm, 8-spored ascospores: hyaline, simple, broadly ellipsoid to almost globose, 10-13 x 9-11 µm Pycnidia: numerous, very small (40-60 µm across), with sunken mouth visible from above as irregular tiny black spots conidia: bacilliform, straight, 7.5-12 µm long Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on Staurothele species and becoming epilithic over carbonate rock World and Sonoran distribution: known from Coconino, Gila, and Yavapai Counties in Arizona and San Bernardino County in southern California. Notes: There are three lichenicolous Verrucaria species on Staurothele which share the following features: areolate thalli, whitish gray, roughly pruinose areoles, and stipe-like attachment organs. Verrucaria bernardinensis is morphologically indistinguishable from Verrucaria inficiens, but differs clearly in having subglobose spores and longer conidia. Verrucaria cetera is readily distinguished by larger spores and in having its perithecia encircled by an involucrellum. (A fourth parasitic species on Staurothele, Verrucaria zamenhofiana, cannot be confused with these species on account of its brown thallus and different growthform). Very similar in general aspect is Verrucaria bernaicensis with which V. bernardinensis shares its small, subglobose spores, but the former species is independent, has epruinose areoles, shorter conidia, and smaller perithecia.