Description: Thallus crustose, thinly episubstratic, sometimes poorly evident, continuous to rimose, whitish or grey. Apothecia lecanorine only when young, later biatorine, 0.2-0.5 mm across, sessile, with a convex, pale to dark brown, often black-dotted disc, and a thin, soon excluded thalline margin. Exciple of radiating hyphae, without algae or with a few algae at the base only; epithecium patchily brown black, without crystals; hymenium colourless, 35-55 μm high; paraphyses lax in K, with distinctly swollen, brown-black apical cells; hypothecium colourless. 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, narrowly ellipsoid, 8-15 x 3-4.5 μm, often guttulate and appearing 1-septate. Pycnidia black, semi-immersed. Conidia 2-4 × 1.5 μm. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a mainly boreal-montane lichen found on lignum and acid bark in upland areas; it belongs to a poorly known group and is widespread in Scandinavia, being also known from the British Isles, France, central Europe, and the mountains of the Iberian Peninsula; perhaps more widespread in the Alps.