Distribution: N - Frl, TAA (Watson 2014), Lomb, Piem (Morisi & Sereno 1995, Isocrono & al. 2004, Morisi 2005), VA (Borlandelli & al. 1996, Piervittori & Isocrono 1997, 1999, Watson 2014), Emil (Nascimbene & al. 2021). C - Sar. S - Cal (Puntillo 1996), Si (Merlo 2004b, Puglisi & Cataldo 2019).
Description: Thallus crustose-placodioid, episubstratic, loosely attached, 1.5-5(-10) mm thick, white to cream-colored, more rarely ash-grey or greyish brown, turning pink in the herbarium, usually epruinose, forming regular or irregular rosettes, areolate in central parts. Central areoles up to 1 mm in diam., discrete, flat to convex, often mixed with elongated lobes; marginal lobes 3-5(-8) mm long, 0.5-1(-1.3) mm wide, contiguous to overlapping, flat to usually strongly convex or almost cylindrical, incised-lobed. Upper cortex paraplectenchymatous, brownish, inspersed with dark brown granules soluble in K, and with coarse hyaline granules insoluble in K, and overlain with a c. 15 µm thick epinecral layer; medulla white, loose to almost hollow, with hyaline granules insoluble in K; lower cortex paraplectenchymatous. Apothecia lecanorine, usually crowded and deformed in thallus center, 0.4-1.5(-2.5) mm across, sessile or somewhat stalked, with a dark reddish brown to black, flat to convex disc, and an entire, raised, 0.2-0.3 mm wide thalline margin. Thalline exciple corticate, 20-40 µm thick; medulla paraplectenchymatous, of thick-walled hyphae, with hyaline, coarse granular crystals insoluble in K; epithecium greenish brown, with superficial hyaline granules insoluble in K; hymenium colourless, 70-80 µm high; paraphyses coherent, c. 2.5 µm thick at mid-level, the upper 3-4 cells submonilliform; hypothecium colourless. Asci 8-spored, oblong-ellipsoid, the thin outer coat K/I+ blue, the wall and apical dome K/I-. Ascospores 1-celled, hyaline, short-elllipsoid, 11-16 x 5-8(-10) µm. Pycnidia black. Conidia hyaline, bacilliform, aseptate, 4-8 x c. 1 µm. Photobiont chlorococcoid. Spot tests: thallus K+ yellow turning red, C-, KC-, P+ orange. Chemistry: norstictic and consstictic or salazinic acids.
Note: a widespread species with an apparently disjunct distribution in mountain areas of the Northern Hemisphere, found on compact siliceous rocks wetted by rain in upland areas; locally abundant only in the Alps, wherever appropriate substrata are available.