Thallus: crustose, granular to irregularly granular-areolate or areolate, effuse, sometimes almost disappearing or endolithic, up to 0.5 mm thick areoles: mostly sharply angular, sometimes dissolved into a powdery (leproselike) crust upper surface: glaucous-white, reddish white, whitish gray or pale brownish gray, not discolored when wet, dull, smooth to rugulose, epruinose upper cortex: sometimes present but not well-developed, composed of paraplectenchymatous cells, 20-50 µm thick, overlain by an epinecral layer up to c. 20 µm thick, without crystals medulla: not developed algal layer: irregular, 50-150 µm thick; algal cells: 8-15 µm in diam. Apothecia: numerous, scattered to crowded and deformed, rarely almost semiglobose, broadly sessile, up to 0.8 mm diam. disc: reddish brown to black, when moist becoming slightly paler and +dark-spotted, with a dark-pigmented edge, plane to moderately convex, pale gray-white pruinose margin: thalline, concolorous with the thallus, narrow (< 0.1mm wide), level with disc, often becoming excluded and disappearing completely amphithecium: with an differentiated algal layer and in part, a narrow, algal-free cortical zone, overlain by a thin epinecral layer up to 10 µm thick, at times overlain by a thick crystalline layer such that no differentiated cortical zone is visible parathecium: sometimes visible from above, narrow to wide, up to c. 70 µm wide toward the outer edge, ±prosoplectenchymatous, long-celled towards outer part and strongly encrusted with dark brown pigment epihymenium: medium brown to brown-black, spotted, occasionally partly extending deeper into hymenium along the conglutinate paraphyses; epipsamma: richly present hymenium: hyaline below, 5580 µm tall; paraphyses: unbranched, 2-2.5 µm wide below, apically strongly clavately swollen (up to 6 µm wide), coherent in groups due to epipsamma, in a gelatinous matrix; hypothecium: hyaline, unoriented hyphae, up to 70 µm thick in center asci: clavate, Bacidia-type, 35-50 x 10-12 µm, 8-spored ascospores: hyaline, 1-septate, narrowly to somewhat broadly ellipsoid, or oblong-fusiform, straight, not constricted at septum, (8-)10-13(-15) x (4-)4.5-5.5(-6) µm, thin-walled Pycnidia: rare, immersed, dark-brown black around the ostiole; conidiogenous cells: elongate, c. 10 x 2 µm conidia: filiform, mostly strong arcuate, 12-20 x 0.8 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on calcareous and non-calcareous rocks, mortar or walls (brick), caliche or rarely shells, coastal and inland World distribution: widely distributed in Europe, northern Africa, western Asia and North America Sonoran distribution: southern California including the Channel Islands and Baja California Sur. Notes: Lecania turicensis is a rather variable species. On limestone the thallus is mostly coherent, areolate with a powdery upper surface, but on siliceous rocks, it is often dissolved into scattered squamules, although the thallus can also be absent. Through regeneration of damaged hymenia, the apothecia are often almost immersed (not seen in Sonoran specimens), irregularly formed and lack the typical pruina. Lecania turicensis is easily overlooked for Lecanora species such as L. crenulata, etc.). The distinguishing features of L. turicensis are its apothecia with a whitish amphithecium, that often becomes excluded, its pruinose discs, and its white-gray thallus. Other species in the Sonoran region, with which it can be confused, are L. chalcophila, L. arizonica, L. rabenhorstii, and L. ryaniana; however, none of them has the combination of pruinose apothecia, a margin becoming excluded and a glaucous thallus (for further notes see under those species).