Distribution: N - TAA. C - Sar (Scheidegger 1993).
Description: Thallus crustose, episubstratic, rimose to verrucose, up to more than 1 mm thick, whitish; medulla white, slightly amyloid, 1+ violet. Apothecia black, lecideine, 0.5-0.8 mm across, broadly sessile, with a flat disc and a thick, persistent proper margin. Proper exciple thin, aethalea-type, the inner hyphae hyaline, prosoplectenchymatous, the outer hyphae parallel and usually strongly brown-pigmented, N-; epithecium olive to brown; hymenium colourless, without oil droplets, 65-85 µm high; hypothecium dark brown. Asci 8-spored, Bacidia-type. Ascospores 1-septate, dark brown, oblong, constricted at septum, 13-16 x 6.5-5.8 µm, Buellia-type, with a microrugulate to rugulate ornamentation. Pycnidia flask-shaped, black, immersed in thallus. Conidia bacilliform, 5-7.5 µm long. Photobiont chlorococcoid. Spot tests: thallus K+ yellow, C-, KC-, P- or P+ faintly yellow; medulla K-, P+ red. Chemistry: cortex with atranorin, medulla with psoromic acid.
Note: a rarely collected lichen of porous siliceous rocks rich in minerals, both in the Mediterranean area and in dry-continental Alpine valleys, where it exceptionally reaches the subalpine belt.