Distribution: N - VG (Castello 2002, Martellos & Castello 2004), TAA, Lomb (Delucchi & Valcuvia 2004), Piem (Morisi & Sereno 1995, Isocrono & al. 2004), Emil (Fariselli & al. 2020), Lig (Brunialti & al. 1999). C - Tosc, Umb (Panfili 2000, Ravera & al. 2006), Laz (TSB 31408), Abr (Nimis & Tretiach 1999), Sar (Rizzi & al. 2011, Giordani & al. 2013, Neuwirth 2018). S - Pugl (Nimis & Tretiach 1999), Bas (Nimis & Tretiach 1999), Cal (Nascimbene & al. 2021), Si (Grillo 1998, Grillo & Caniglia 2004, Cataldo & Cannavò 2014).
Description: Thallus crustose, white to ochraceous, not pruinose, rimose or areolate, sometimes warted, forming small patches (1-2 cm diam.). Cortex colourless to pale grey, without distinct structure; medulla white. Apothecia lecideine, first immersed, then subsessile, 0.2-0.7 mm across, with a flat to convex, usually not pruinose, black disc, a thin, often poorly visible proper margin, and sometimes a pseudothalline margin in young apothecia. Proper exciple brown in outer part, paler brown within; epithecium brown; hymenium 55 110 μm tall, colourless, KI+ blue; paraphyses simple, capitate, 1-2 μm wide at base, 4-5 μm wide at apex; hypothecium pale to 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, approaching the Bacidia-type. Ascospores 5-septate to submuriform, usually with 3 transverse septa and 1-2 longitudinal septa, brown, ellipsoid, thick-walled, 15-20(-27) x 7-12 μm. Photobiont chlorococcoid. Spot tests: cortex K-, C-, KC-, P-, UV-; medulla K+ red, C-, KC-, P+ yellow-orange, UV-. Chemistry: medulla with norstictic acid.
Note: a temperate, perhaps holarctic early coloniser of basic siliceous rocks and roofing tiles; overlooked, and certainly more widespread.