Description: Thallus crustose, episubstratic, continuous or rimose, more or less glossy, pale grey or grey-green, without a distinct prothallus. Medulla white, I-. Apothecia lecideine, 0.3-0.7(-1.2) mm across, sessile, reddish brown to brown-black, with a concave to slightly convex disc and a raised, persistent proper margin. Proper exciple dark reddish brown in outer part, pale reddish brown to colourless within; epithecium colourless or brownish, K-; hymenium colourless, but usually inspersed with blue-violet granules reacting K+ green, 65-90 µm high; paraphyses simple or sparingly branched and anastomosing in upper part, c. 1.5 µm thick at mid-level, the apical cells up to 3 µm wide, without a dark cap; hypothecium dark reddish brown, often with blue-violet granules. Asci 8-spored, clavate, with a I+ blue tholus and an internal, darker I+ tubular structure, the external gel I+ faintly blue, Porpidia-type. Ascospores 1-celled, hyaline, ellipsoid, 12-17 x (5-)6-7(-9) µm. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: thallus without lichen substances.
Note: on periodically inundated siliceous rocks in lowland areas. The record from Italy (see Nimis 1993: 377) is dubious.