Description: Thallus crustose, fully endolithic, poorly evident. Apothecia lecideine, 0.3-0.7 mm across, deeply immersed in pits in the rock, with a flat, black disc (sometimes thinly white pruinose) and a thin, black, persistent proper margin. Epithecium red-brown; hymenium colourless, I+ partly pale blue; paraphyses branched and slightly anastomosing, septate, scarcely swollen at apex; hypothecium brown, I-. Asci 8-spored, elongate-clavate, Porpidia-type. Ascospores 1-celled, hyaline, ellipsoid, 10-19 x 6-9 µm, with a gelatinous perispore when young, and with a warted ornamentation when old. Photobiont chlorococcoid. Spot tests: all negative. Chemistry: no lichen substances.
Note: a widespread, temperate to southern boreal-montane lichen found on a wide variety of calciferous rocks, especially limestone, with a wide altitudinal range.