Description: Thallus crustose, episubstratic, consisting of scattered to clustered, reddish brown, sometimes faintly pale-striate, 0.3-1.8(-2) mm wide, angular, swollen, convex areoles, or reduced to the thalline margin of the apothecia. Algal layer even, continuous. Apothecia lecanorine, 0.2-0.6(-1) mm across, 1(-3) per areole and occupying most of its surface, with an , oblong or kidney-shaped, smooth, sometimes umbonate, deep red-chestnut brown disc, and a usually paler, thick, raised, smooth or sometimes white-striate thalline margin. Epithecium brownish; hymenium colourless, 70-100(-120) µm high; paraphyses 1.5-2 µm thick at base, the apical cells 2-4 µm wide; hypothecium colourless. Asci c. 200-spored, clavate, the apical dome K/I-. Ascospores 1-celled, hyaline, ellipsoid to subcylindrical, 4-6 x 1-2.5 µm. Photobiont chlorococcoid. Spot test: cortex K+ yellow then red (needle-like crystals), C-, KC-, P- or P+ yellowish. Chemistry: norstictic acid.
Note: on hard siliceous rocks, especially granite, near the coast. A Mediterranean-Atlantic European species, reported from a few localities, from the British Isles to Portugal, and also known from the Aegean Islands.