Thallus: areolate to verrucose, 0.4-0.7(-1) mm thick, with broad fissures areoles: irregular in outline, 0.5-1.2 mm wide surface: pale brown to medium brown, smooth anatomy: , 10-20 µm thick; upper cortex: poorly defined, overlain with an amorphous, hyaline epinecralic layer; algal layer: paraplectenchymatous in upper part, composed of cells 4-7 µm in diam., 100-200 µm thick, lower part subparaplectenchymatous, with algal cells 6-12 µm in diam.; medulla: subparaplectenchymatous, partly with filamentous hyphae, interspersed with rock fragments and crystals Perithecia: immersed, with upper part emergent and bare; exciple: pyriform, with a rather long neck, 0.35-0.45 mm wide and 0.45-0.60 mm high, pale to brown-black; involucrellum: completely enveloping the exciple, with upper half notably thicker (80-130 µm) than lower (40-60 µm); periphyses 35-50 µm long, sparingly branched asci: broadly clavate, 90-105 x 27-40 µm, 8-spored ascospores: hyaline, simple, broadly ellipsoid, 25-30 x 14-17 µm Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: epilithic, on a superficially partly calciferous rock, montane World and Sonoran distribution: known only from the type collection in Arizona. Notes: Verrucaria incrassata resembles V. murorum, but the involucrellum is markedly different: completely enclosing the exciple with the upper half notably thickened in V. incrassata, covering only the upper half of the exciple in V. murorum.