Description: Thallus crustose, of variable thickness, endo- to episubstratic, continuous to rimose-areolate, whitish to grey; cortex overlain with a thin epinecral layer inspersed with crystals; medulla strongly amyloid, I+ violet. Apothecia lecideine, black, 0.5-1.2 mm across, sessile and constricted at base, with a flat to convex disc, and a thick, prominent, persistent proper margin. Proper exciple c. 100 µm wide, of intricate hyphae, homogeneously dark brown to black, with an additional orange pigment reacting K+ reddish (solution), the inner part with textura intricata, the outer part with textura oblita, leptocline-type; epithecium brown; hymenium colourless, not inspersed with oil droplets, c. 75 µm high; hypothecium dark brown. Asci 8-spored, Bacidia-type. Ascospores 1-septate, brown, oblong, not constricted at septum, 12-16 x 7.5-8.5 µm, Physconia-type, wirh a rugulate, more rarely psilate ornamentation, rarely smooth when very young. Pycnidia black, immersed in thallus. Conidia bacilliform, 4-5 µm long. Photobiont chlorococcoid. Spot tests: thallus K+ yellow, C-, KC-, P- or P+ very faintly yellow. Chemistry: atranorin.
Note: a mainly boreal-montane species found on steeply inclined to underhanging surfaces of hard siliceous rocks in upland areas. Earlier records (Nimis 1993: 140) from central and southern Italy, plus that from Sicilia by Grillo (1998) could refer to other related species (B. halonia, B. sardiniensis, B. saxorum, B. sejuncta and B. subdisciformis), and are not reported here.