Description: Thallus crustose, episubstratic, areolate, brown to ochre-coloured, often glossy, without a distinct prothallus, the areoles small, angular, contiguous, with a smooth surface. Cortex of anticlinally arranged, cellular hyphae, the terminal cells swollen, with brown caps; medulla white, I-. Apothecia biatorine or cryptolecanorine, immersed in the areoles, black, 0.15-0.3 mm across, with a flat to convex disc and a thin, soon excluded proper margin. Proper exciple poorly differentiated, aethalea-type, the inner hyphae narrow, hyaline, prosoplectenchymatous, the outer hyphae parallel, moderately swollen and usually strongly carbonized with brown and aeruginose pigments reacting N+ violet; epithecium brown; hymenium colourless, without oil droplets, c. 60 µm high; hypothecium dark brown. Asci 8-spored, clavate to cylindrical-clavate, the apical dome K/I+ dark blue with a pale, conical-pointed apical cushion (axial mass), the wall I-, but the thin outer gel I+ blue, Bacidia-type. Ascospores 1-septate, broadly oblong, not constricted at septum, 10-12 x 5-6 µm, Buellia-type, thin- and smooth-walled throughout. Photobiont chlorococcoid. Spot tests: K-, C-, KC-, P-, UV-. Chemistry: 2'-O-Methylperlatolic acid.
Note: on vertical to underhanging surfaces of siliceous rocks near the ground in warm-dry situations, such as in arid grasslands and in openings of Mediterranean garrigues; known only from the eastern Alps and the Pyrenees. Related to, and perhaps a synonym of B. tirolensis (see Bungartz 2004), but chemically different, this taxon needs further study.