Thallus: strongly rimose to regularly cracked-areolate, thin to moderately thick (up to 0.2 mm), up to several centimeters wide, not subgelatinous when wetted, without a prothallus areoles: plane, 0.3-0.5 mm wide surface: gray-brown to dark brown, smooth anatomy: upper cortex: paraplectenchymatous, composed of cells 3-7 µm in diam., thin (7-15 µm), colorless; algal cells: 5-10 µm in diam., irregularly dispersed throughout most of thallus; medulla indiscernible Perithecia: one to several in each areole, immersed in thallus with only the apical portion emergent; exciple: subglobose, 0.20-0.25 mm wide, colorless to brown, c. 20 µm thick; involucrellum: extending down to lower part or base-level of the exciple, closely appressed to the exciple or somewhat spreading; periphyses c. 25 µm long, rather thickish asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid , 20-25 x 10-12 µm Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: epilithic, on both siliceous and limestone rocks in montane sites in or along streams World distribution: northern Eurasia and North America Sonoran distribution: one collection from southern California (Mt. Palomar). Notes: Among the freshwater species, Verrucaria aethiobola is recognized by its diffusely pigmented involucrellum (not of Zellnetz type). Verrucaria praetermissa, which has also a non-gelatinous thallus and spores of similar size, differs in its wider spreading involucrellum with clear pigmentation (Zellnetz type), and narrower ascospores.