Distribution: N - Ven, TAA (Caniglia & al. 2002, Thor & Nascimbene 2007, 2014, Nascimbene & al. 2007b, 2008c, Nascimbene 2008b, 2013), Lomb, Piem (Isocrono & al. 2004), Emil (Fariselli & al. 2020), Lig (Giordani & al. 2009, Giordani & Incerti 2008). C - Tosc, Marc (Nimis & Tretiach 1999), Abr (Nimis & Tretiach 1999), Mol (Nimis & Tretiach 1999, Caporale & al. 2008). S - Camp (Aprile & al. 2003b), Bas, Cal (Puntillo 1996, van den Boom & Giralt 2002, Puntillo 2011), Si.
Description: Thallus crustose, often poorly developed and inconspicuous, endosubstratic or thinly granular, whitish or olivaceous grey. Apothecia biatorine, black (bluish black when wet), adnate to partly immersed, 0.2-0.6(-0.8) mm across, with a flat to convex, sometimes thinly white-or bluish-pruinose, often uneven disc (especially when young), and a soon excluded proper margin. Proper exciple of coherent, radiating hyphae, dark greenish brown in outer part, colourless within; epithecium olive-black to blue-green, K+ intensifying green, N+ reddish, with minute granules dissolving in K; hymenium with violet, brownish or greenish vertical streaks reacting K+ green, 30-60 µm high, I+ blue; paraphyses sparingly branched and anastomosing, 1.3-2 µm thick at mid-level, the apical cells not much swollen, but sometimes with a dark brown, to 5 µm wide cap; hypothecium colourless to pale yellowish brown, sometimes orange-brown in upper part. Asci 8-spored, broadly clavate, Lecanora-type. Ascospores 1-celled (rarely a few 1-septate), hyaline, oblong to ellipsoid, 6-10(-14) x 2.5-4.5(-6) μm. Pycnidia black, immersed, the wall green-brown, K+ green. Conidia short-bacilliform, arising laterally and terminally, 3-4 x 1.5-18 μm. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: thallus with placodiolic acid.
Note: on hard lignum, more rarely on bark of conifers; most common in the Alps, but also present in the mountains of southern Italy, especially in old Castanea woodlands. According to Printzen (1995) the systematic position of this species is not clear; it certainly does not belong to Lecidea s.str.