Description: Thallus crustose, endosubstratic or thinly episubstratic, continuous ro rimose, grey or yellowish grey. Apothecia lecanorine, 0.2-1.2 mm across, with a flat, orange-brown or yellowish brown, strongly to weakly pruinose disc, and a thin, finally usually excluded thalline margin. Thalline exciple ecorticate, with many small crystals soluble in K; epithecium grey-brown, with many small crystals soluble in K; hymenium colourless, 60-75 µm high; hypothecium colourless. Asci (8-)12-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, 10-13 x 5-7.5 µm. Photobiont chlorococcoid. Spot tests: thallus and apothecial margin K+ yellow, C-, KC-, P+ yellow (apothecial margin only). Chemistry: thallus and apothecial margin with atranorin, chloratranorin and zeorin; apothecial margin with additional psoromic and 2'-0-demethylpsoromic acids.
Note: this is a member of the L. albella-group, which includes species with a pruinose disc and an ecorticate apothecial margin. It is distinguished by the polysporous asci and the P+ yellow apothecial margin (psoromic acid), and has a mainly northern distribution in Europe, growing on bark in rather shaded and humid situations. The Italian distribution follows Jatta (1909-1911) who provides a description fitting the essential characters of the species, but the presence of this species in Italy requires re-confirmation.