Thallus: crustose, rimose-areolate or verrucose-areolate, verrucose or verruculose; prothallus: not visible areoles: thin or thick, opaque or glossy, ecorticate surface: yellowish white to yellowish gray or whitish gray to gray or orange-gray to brown-gray, smooth, epruinose, with an indistinct margin, esorediate Apothecia: subimmersed when young, sessile when mature or sessile or constricted at the base to almost subpedicilate, 0.7-1.2 mm in diam., lecanorine disc: dark brown to blackish brown, plane, epruinose margin: concolorous with thallus, thin or thick, persistent, even or prominent, entire or flexuose, smooth, entire or verruculose or crenulate, without a parathecial ring amphithecium: present, with numerous algal cells, with large crystals insoluble in K, corticate; cortex: hyaline, indistinct, uniform or basally thickened, gelatinous or interspersed, 20-50 µm thick laterally, (20-)25-40(-65) µm thick basally parathecium: hyaline, containing crystals soluble in K epihymenium: blackish brown to greenish black (turning green in K), color of pigmentation altering in K, without crystals hymenium: hyaline, clear; paraphyses: not thickened or slightly thickened (up to 2.5 µm wide) apically, olivaceous; subhymenium: hyaline, 15-20 µm thick; hypothecium: hyaline, without oil droplets asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid, (12-)12.5-13(-15) x (6-)7-8.5(-9) µm; wall: less than 1 µm thick Pycnidia: immersed, cerebriform; conidiophores: type II sensu Vobis conidia: filiform, (13-)14-15.5(-17) µm long Spot tests: thallus and apothecial margin K+ yellow, C-, KC-, P+ pale orange Secondary metabolites: atranorin (major), chloroatranorin (minor), 4-dechlorogangaleoidin (minor), gangaleoidin (major), leoidin (submajor), norgangaleoidin (minor) and ±skyrin (minor). Substrate and ecology: on exposed siliceous rocks, common in coastal areas, but also present in montane areas further inland World distribution: Africa, Europe, and North America Sonoran distribution: Arizona, southern California Baja California, and Baja California Sur. Notes: Lecanora gangaleoides is recognized by its black apothecial discs, its egraulose greenish epihymenium, and the presence of the gangaleoidin chemosyndrome. Lecanora gangaleoides resembles L. argentea; the differences are discussed under the latter species. Morphologically L. gangaleoides resembles Tephromela atra (Hudson) Hafellner, which is readily distinguished by the purple hymenium color.