Description: Thallus crustose, endosubstratic to thinly episubstratic, often poorly evident, grey to dark grey brown, thin, smooth to granulose. Cortex with crystals arranged in anticlinal rows, visible under polarized licht; medulla white, I-. Apothecia lecanorine, round, sessile, strongly constricted at base, 0.5-1.5(-4) mm across, with a dark brown to blackish brown, initially concave and faintly grey-pruinose, then flat to slightly convex disc, and a concolorous or paler, glossy, thick, smooth, crenulate thalline margin. Thalline exciple cupular, reddish brown in outer part, colourless within, not inspersed with granules; proper exciple poorly developed; epithecium yellowish brown, K-, N-; hymenium colourless, 40-80 μm high, K/I+ blue; paraphyses simple, distinctly thickened above, coherent, the apical cells brown-capped. Asci 8-spored, broadly clavate, the K/I+ blue tholus penetrated by a faintly amyloid apical cushion with parallel or diverging flanks, the wall K/I-, surrounded by a K/I+ blue outer layer, Lecanora-type. Ascospores 0(-2-6)-septate (the septation unclear in squash preparations), hyaline, ellipsoid-cylindrical, thick-walled, straight to curved, (20-)29-39(-42) x (4-)5-6.5(-8) μm. Photobiont chlorococcoid. Spot tests: thallus K- or K+ reddish brown (needle-like crystals), C-, KC-, P- or P+ pale yellow, UV-. Chemistry: variable amounts of norstictic acid.
Note: an arctic-alpine, circumpolar lichen found on bryophytes (e.g. Andreaea, Grimmia) in sites with periodic seepage of water, with optimum above treeline on siliceous substrata.
Growth form: Crustose
Substrata: soil, terricolous mosses, and plant debris