Distribution: N - TAA (B-180942). C - Sar (Scheidegger 1993).
Description: Thallus crustose, episubstratic, granular to bullate, whitish, delimited by a black prothallus, growing on the thalli of other crustose lichens; medulla strongly amyloid, I+ violet. Apothecia lecideine, black, 0.5-1 mm across, sessile and constricted at base, with a flat to strongly convex disc and a thin, finally excluded proper margin. Proper exciple radially formed, dark brown, the inner part of textura oblita, the outer of textura angularis, dispersa-type; epithecium brown; hymenium colourless, without oil droplets, c. 85 µm high; hypothecium dark brown. Asci 8-spored, Bacidia-type. Ascospores 1-3-septate (pluriseptate only when overmature), brown, narrowly oblong, not constricted at septum, 15-30 x 7-10 µm, Buellia-typc, with a rugulate ornamentation. Pycnidia black, immersed in thallus. Conidia bacilliform, 5-5.7 µm long. Photobiont chlorococcoid. Spot tests: thallus K+ yellow turning red (with crystals), C-, KC-, P- or P+ faintly yellow. Chemistry: atranorin, norstictic acid with connorstictic acid, stictic acid with cryptostictic, constictic and menegazziaic acids.
Note: a mainly Mediterranean species of granitic rocks, also occurring in the Alps in warm-dry situations.