Thallus: crustose, verrucose-areolate or dispersed-areolate, verrucose or verruculose; prothallus: not visible areoles: thin or thick, opaque, ecorticate surface: yellowish white to yellowish gray, smooth, epruinose, with an indistinct margin, esorediate Apothecia: constricted at the base to almost subpedicilate, 0.9-2.5 mm in diam., lecanorine disc: dark brown to blackish brown or gray-brown, plane, slightly pruinose or heavily whitish gray pruinose margin: concolorous with thallus, thick, persistent, prominent, not flexuose, smooth or rough, entire or verruculose, without a parathecial ring amphithecium: present, with numerous algal cells, with large crystals insoluble in K, corticate; cortex: hyaline or pale yellow, distinct, basally thickened, gelatinous or interspersed, 20-30 µm thick laterally, 30-45 µm thick basally parathecium: hyaline, containing crystals soluble in K epihymenium: brown to dark brown or blackish brown to greenish black (turning green in K), with pigment dissolving in K, with crystals dissolving in K hymenium: hyaline, clear; paraphyses: slightly thickened apically, not pigmented; subhymenium: hyaline, 15-20 µm thick; hypothecium: hyaline, without oil droplets asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid or broadly ellipsoid, (11.5-)14-16(-16.5) x (6-) 6.5-7.5(-8.5) µm; wall: less than 1 µm thick Pycnidia: not seen Spot tests: K + yellow, C-, KC-, P- or P+ pale yellow Secondary metabolites: atranorin (major), chloroatranorin (minor), gangaleoidin (major), nephrosteranic acid (major), and norgangaleoidin (submajor). Substrate and ecology: on coastal siliceous rocks in xeric supralittoral World distribution: endemic to western North America Sonoran distribution: southern California. Notes: Lecanora californica superficially resembles an Ochrolechia spp. due to the large apothecia, but is readily distinguished by smaller ascospores, hymenial structure, and chemistry. Among Lecanora spp. it is hardly confused with any other species, since it has large apothecia with pruinose discs and a thick margins. The only similar species is L. cenisia that differs in having smaller apothecia with epruinose or slightly pruinose disc, and a different chemistry.