Description: Thallus crustose, thin, white to grey-white, continuous to slightly warted, epruinose, sometimes delimited by a dark prothallus. Apothecia lecanorine, 0.3-1.2 mm across, sessile or slightly constricted at base, with a pale brown, orange-brown to medium brown (rarely darker), epruinose, flat to slightly convex disc, and a thin, smooth, persistent thalline margin which tends to become much thinner with age. Thalline exciple with a 20-30 µm thick cortex inspersed with abundant, very small crystals; medulla rich in algae, with small crystals (2-2.5 µm) intermixed with a few very large crystals (to 40 µm); epithecium almost colourless to grey-brown, the tips of paraphyses with abundant, rather fine crystals soluble in K but usually not in N; hymenium colourless, 80-100 µm high, not inspersed with oil droplets; paraphyses 1.5-2.5 µm thick, the apical cells swollen, 3.5-4 µm wide; hypothecium colourless, not inspersed. Asci 8-spored, clavate, very thin-walled, with a K/I+ blue, tall tholus penetrated by a faintly amyloid apical cushion, the wall K/I-, surrounded by a blue outer layer, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid, 11-17 x 5-8 µm, thin-walled. Photobiont chlorococcoid. Spot tests: thallus and apothecial margin K+ yellow, C-, KC-, P+ yellow. Chemistry: atranorin, chloratranorin, and roccellic acid.
Note: a probably circumboreal-montane lichen found on dead or decaying twigs of shrubs, especially Rhododendron ferrugineum in the subalpine belt; certainly widespread throughout the Alps, much rarer in the Apennines.