Thallus: crustose, very variable, from partially immersed to continuous, rimose or areolate, up to 12 cm in diam, up to 0.4 mm thick, sometimes with an indistinct gray to black prothallus areoles: irregularly shaped, 0.4-0.5(-0.8) mm in diam. surface: white, pale gray, greenish gray or olive, red, rarely orange, rough, rugose cortex: hyaline or occasionally encrusted with orange crystals above, 20-30 µm thick, lacking an epinecral layer medulla: white, I-, with hyphae 3.5-4 µm in diam.; algal layer: 60-65 µm thick with cells 9-10(-14) in diam Apothecia: +round, sessile, constricted at base, 0.1-2(-4) mm in diam. disc: black or brownish black, subconcave to plane or convex, dull, epruinose to weakly grayish or whitish pruinose margin: usually distinct, rarely becoming indistinct, black or occasionally rusty red, entire to rarely flexuose or crenulate exciple: black to dark brown peripherally, brown to dark brown internally, up to 130-200 µm wide (relatively even above and below), with hyphae c. 3-5 µm wide hymenium: hyaline below, pale to olivaceous brown above, I+ blue, 75-140 µm tall; paraphyses: branched and anastomosing, 1.5-1.8 µm wide below, 2.5-4 µm wide apically; hypothecium: pale to dark brown, K+ pale red, up to 300350 µm thick asci: clavate, 60-100 x 13-22 µm, 8-spored ascospores: hyaline, simple, ellipsoid, (13-)16-20(-26) x (5-)6-11.5 µm, halonate Pycnidia: not observed in Sonoran material, elsewhere immersed conidia: hyaline, bacilliform, 7-14 x 1-1.1 µm Spot tests: K- or +yellow, C-, KC-, P- or +orange Secondary metabolites: +stictic and +cryptostictic acids or none detected. Substrate and ecology: on siliceous rocks and boulders, less often on pebbles and very rarely on wood World distribution: throughout temperate and arctic or alpine areas in Europe, Asia, North America, and Australasia Sonoran distribution: in the higher mountains of central and eastern Arizona.