Distribution: N - TAA, Lomb, Piem, VA (Piervittori & Isocrono 1999).
Description: Thallus crustose, episubstratic, coarsely areolate-verruculose to subsquamulose, whitish to brownish white, esorediate. Areoles 0.25-1 mm across, convex, sometimes with raised margins and appearing almost squamulose. Apothecia biatorine, 0.3-1.2 mm across, adnate, not or only slightly constricted at base, reddish brown to cinnamon-brown (old apothecia sometimes almost black), with a convex, often tuberculate disc, and a very thin, paler, soon excluded proper margin. Proper exciple 50-120 µm wide laterally, of radiating hyphae, dark brown ro reddish brown in outer part, colourless or yellowish within; epithecium scarcely differentiated from the hymenium, colourless to pale yellow; hymenium colourless or sometimes brown-striped, 50-80 µm high; paraphyses mostly simple, conglutinated, 1-2.5 µm thick at mid-level, the apical cells to 3 µm wide; hypothecium (incl. subhymenium) 120-360 µm high, colourless or partly pale reddish brown to pale yellow. Asci 8-spored, clavate, with a K/I+ blue apical dome penetrated by a narrow, K/I– apical cushion surrounded by a narrow, deeply K/I+ blue zone, the wall K/I- but surrounded by an I+ red-brown, K/I+ blue outer layer, the ocular chamber relatively small, Biatora-type. Ascospores 1-celled (rarely 1-2-septate), hyaline, narrowly ellipsoid, (10-)13-17(-22) x (3.5-)4.5-5.2(-6) µm, with a thin perispore. Pycnidia very rare, pyriform, colourless. Conidia fusiform or bacilliform, 4-6.5 x c. 0.8 µm. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P+ orange-red. Chemistry: argopsin, norargopsin.
Note: most frequent on soil and plant debris on siliceous substrata in upland areas. According to Printzen (1995) this species is known with certainty only from northern Europe, and western North America, but it has been reported from several localities in the Alps (see e.g. Roux & coll. 2014). Printzen (in litt.), however, thinks that its presence in the Alps is dubious, and most records from this area could refer to B. subduplex.
Growth form: Crustose
Substrata: soil, terricolous mosses, and plant debris