Distribution: N - TAA (Trinkaus & Mayrhofer 2000), Lomb, Piem (Matteucci & al. 2013), VA (Piervittori & Isocrono 1999, Piervittori & al. 2004). C - Sar (Trinkaus & Mayrhofer 2000). S - Pugl, Si.
Description: Thallus crustose-placodioid, episubstratic, of radiating, white-pruinose, 1-2 cm long, 0.3-1.2 mm wide lobes, forming orbicular to irregular, up to 4 cm wide rosettes. Cortex c. 20 μm thick, filled with crystals; medulla white, I-; lower surface pale, attached with rhizohyphae. Apothecia not always present, lecideine, 0.6-1.8 mm across, at first immersed but soon becoming adnate, with a black, flat to slightly convex, soon epruinose disc, and a thin, black, often pruinose, persistent proper margin; a pseudothalline margin is sometimes present at the base of the proper margin. Proper exciple dark red-brown in outer part, paler within; hymenium colourless, not inspersed with oil droplets, 70-150 μm high, I+ blue; paraphyses 1-1.5 μm thick at mid-level, the apical cells 4-5 μm wide, with a brown cap; hypothecium black-brown to black-grey. Asci 8-spored, clavate, Bacidia-type. Ascospores 1-septate, slightly constricted at septum, brown, oblong-ellipsoid, 12-22 x 5.5-10.5 μm, with a thin, distinctly warted wall. Pycnidia black. conidia bacilliform, 5-8 x 1-1.5 μm. Photobiont chlorococcoid. Spot tests: cortex K+ yellow, C-, KC-, P-; medulla K-, P-, or K+ red, P+ orange-red in spots. Chemistry: cortex with atranorin; medulla sometimes with norstictic and stictic acids.
Note: widely distributed in Europe, from submediterranean regions to Scandinavia, on base-rich mineral soil, on weathered gypsum and gypsum soil. South Italian records (Nimis 1993: 138) should be checked: they could refer to B. asterella Poelt & Sulzer.
Growth form: Crustose placodiomorph
Substrata: soil, terricolous mosses, and plant debris
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Subcontinental: restricted to areas with a dry-subcontinental climate (e.g. dry Alpine valleys, parts of Mediterranean Italy)