Description: Thallus crustose, endosubstratic or thinly episubstratic, continuous to rimose or granular, rarely areolate, white to pale brown. Apothecia lecideine, at first often slightly immersed, then broadly sessile and constricted at base, (0.15-)0.2-0.4(-0.6) mm across, with a reddish to dark brown, rarely black, at first flat but soon convex, usually epruinose disc, and a thin, slightly raised, entire, often finally excluded proper margin. Proper exciple pale to dark brown and K+ purple at outer edge, pale brown to colourless within, of conglutinated hyphae; epithecium pale to dark brown, 6-15 μm high, K-, N-; hymenium colourless, 40-60(-70) µm high, I+ blue, then wine-red; paraphyses simple, easily made free, 1.4-2.2 μm thick at base, the apical cells capitate, up to 5.5 μm wide, with a dark brown pigment located within the cell walls; hypothecium more or less colourless, 50-130 μm high. Asci 8-spored, cylindrical-clavate, with a K/I+ blue outer coat and a K/I+ uniformly blue apical dome, Catillaria-type. Ascospores 1-septate, hyaline, oblong or oblong-ellipsoid, 7-10(-12) x (2-)2.5-3.5(-4) µm. Pycnidia globose-ovoid, the wall brown (cells with dark caps). Conidia ellipsoid to short-cylindrical, 2-3.5 x 0.7-1.3 µm. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a mainly mild-temperate lichen found on limestone, more rarely on dolomite, sometimes on nutrient-enriched, base-rich siliceous rocks, with optimum in open woodlands but present also inside conurbations as well, and on monuments in archaeological areas, with a wide altitudinal range.