Description: Thallus small-squamulose to subcrustose and warted-granular, whitish grey to grey, darker in the centre of the squamules, forming patches to 4 cm in diam. Squamules flattened, crenate to lobulate, smooth, contiguous to more or less overlapping, 0.1-0.5(-1) mm broad, forming a compact crust. Upper cortex 5-10 µm thick, overlain by an epinecral layer; algal layer with scattered groups of algae often arranged in columns; medulla white, 15-50 µm thick. Apothecia frequent, lecideine, sessile, often aggregated, 0.3-0.8(-1) mm across, with a black to brown-black, convex disc and an indistinct, soon excluded proper margin. Exciple of radiating hyphae, pale in outer part, red-brown within, K+ intensifying, N+ purple-red; epithecium pale greenish grey, K-, N+ reddish; hymenium colourless, 70-90 µm high; paraphyses mostly simple, adglutinated, 1.5-3 μm thick at mid-level, the apical cells up to 5 μm wide; subhymenium 50-75 μm high, mostly colourless in upper part, pinkish brown to dark brown in lower part; hypothecium brown-red in upper part, paler in lower part. Asci 8-spored, cylindrical-clavate, with a K/I+ blue apical dome penetrated by a narrow, K/I– apical cushion surrounded by an indistinct, apically often tapering, wall K/I– but surrounded by an I+ red-brown, K/I+ blue outer layer. Ascospores (0-)1-3-septate, hyaline, fusiform and pointed at one end, with a gelatinous coat, 12-25(-34) x 3-5(-6) µm. Photobiont chlorococcoid. Spot tests: thallus and medulla K-, C-, KC-, P-, UV-. Chemistry: thallus with zeorin.
Note: a cool-temperate to arctic-alpine, circumpolar lichen found on terricolous mosses and bare calciferous soil, most frequent in upland areas, from the Alps to the high Mediterranean mountains.
Growth form: Crustose
Substrata: soil, terricolous mosses, and plant debris