Thallus: crustose, continuous or rimose-areolate; prothallus: white areoles: flat, thin, opaque, ecorticate surface: yellowish white to yellowish gray or whitish gray to gray or pale green to greenish white, smooth, epruinose; with an indistinct or zonate margin, esorediate Apothecia: subimmersed when young, sessile when mature or sessile, 0.4-1.4 mm in diam., lecanorine disc: red-brown, plane, epruinose margin: concolorous with thallus, thick, persistent, even, not flexuose, rough, entire or verrucose or verruculose, without a parathecial ring amphithecium: present, with numerous algal cells, with large crystals insoluble in K, corticate; cortex: indistinct, basally not thickened, gelatinous or interspersed, hyaline, (15-)20-25(-30) µm thick parathecium: hyaline, containing crystals soluble in K epihymenium: without crystals, with pigment not dissolving in K hymenium: hyaline, clear; paraphyses: red-brown to orange-brown, slightly thickened (up to 3 µm wide) apically; subhymenium: hyaline, 15-20 µm thick; hypothecium: hyaline, without oil droplets asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid, (10-)10.5-14.5(-15) x (5-)5.5-7.5(-8) µm; wall: less than 1 µm thick Pycnidia: immersed, cerebriform; conidiophores: type II sensu Vobis conidia: filiform, 15-18 µm long Spot test: thallus and apothecial margin K+ yellow, C-, KC-, P+ yellow Secondary metabolites: containing atranorin (major), chloroatranorin (trace), zeorin (major) and traces of unidentified terpenes. Substrate and ecology: on somewhat shaded siliceous rocks World distribution: subcosmopolitan, known from Asia, Australasia, North and South America Sonoran distribution: Arizona, Chihuahua and Sonora. Notes: Lecanora subimmergens is characterized by its egranulose epihymnium, large amphithecial crystals, the presence of zeorin, and the continuous to rimose thallus. It is similar to L. campestris, but readily distinguishd by its large amphithecial crystals. Morphotypes of L. pseudistera may also be simlar, but can be distingished by the presence of the 2'-O-methylperlatolic acid chemosyndrome, the absence of zeorin, and the verrucose thallus.