Thallus: crustose, areolate, verruculose or bullate, thin or up to 1.2 mm thick; prothallus: absent surface: white (like chalk), or yellowish white to whitish gray, dull to weakly glossy; without soredia or isidia Apothecia: sessile or sometimes semi-immersed, strongly constricted at base, 1-2 mm in diam. disc: black, plane, convex to strongly convex (when old), epruinose margin: distinct, thin (c. 0.1 mm wide), becoming excluded exciple: bluish to greenish black, without algal cells parathecium: reddish brown to rarely yellowish brown, without crystals epihymenium: green, or rarely olive (if damaged ?) hymenium: hyaline, 60-85 µm tall, not inspersed; paraphyses: simple, rarely anastomosing or branched, not or slightly or sometimes distinctly thickened apically hypothecium: brown, yellowish brown, or with reddish brown hyphal ropes stretching into the exciple asci: clavate, lecanoral, 8-spored ascospores: hyaline, simple, broadly ellipsoid to ovoid, 8-16 x 5-9 µm; wall: thick and smooth, not halonate Pycnidia: globular, with a brown wall, at upper side blackish brown, with Vobis-type III conidiophores conidia: filiform, strongly curved, 15-30 µm long Spot tests: thallus surface K+ yellow to rarely K-, C-, KC-, P+ yellow to rarely P- Secondary metabolites: 4,5-dichloro3-O-methylnorlichexanthone and rarely arthothelin (2,4,5trichloronorlichexanthone), atranorin, chloroatranorin, diploicin, and thuringione (=2,4,5-trichloro-3-O-methylnorlichexanthone). Substrate and ecology: on non-calciferous rocks, rarely wood or bark World distribution: Africa, and temperate parts of Asia, Europe, North and South America Sonoran distribution: widespread in interior region of Arizona, southern California, Baja California and Sonora at intermediate elevations.