Distribution: N - VG, TAA, Piem, VA (Piervittori & Isocrono 1999), Lig (Roccardi 2006). C - Tosc, Umb (Genovesi 2003b, 2011, Ravera & al. 2006), Laz (Bartoli 1997b, Genovesi & al. 2011), Mol (Garofalo & al. 1999, Caporale & al. 2008), Sar (Rizzi & al. 2011, Giordani & al. 2013). S - Camp (Garofalo & al. 1999, Ricciardi & al. 2000, Aprile & al. 2002, Nimis & Tretiach 2004), Pugl (Nimis & Tretiach 1999), Bas (Nimis & Tretiach 1999), Cal (Puntillo 1996), Si (Nimis & al. 1996b, Ottonello & Puntillo 1995, Ottonello & Romano 1997, Grillo 1998, Grillo & Caniglia 2004, Ottonello & al. 2011).
Description: Thallus crustose to subsquamulose, epilithic, areolate, often forming extensive patches to 13 cm diam. Areoles 0.5-3 mm diam., usually of different sizes in the same thallus, attached by the entire lower surface, scattered to contiguous, flat to convex, angular in the center, often sublobate at margins, brown with usually a darker rim, more or less densely white-pruinose (densely pruinose thalli appear white, sparingly pruinose thalli brown). Algal layer continuous; medulla white. Apothecia indistinctly lecanorine, 0.1-0.4 across, 1-5 per squamule, immersed, often coalescing, with a round to angular, concave to flat, smooth, brown, often white-pruinose disc and an inconspicuous thalline margin; proper margin brown-black, contrasting with the paler disc. Proper exciple 8-14 μm thick at base, to 30 μm in upper part, yellowish; epithecium brown; hymenium colourless, 85-110(-135) μm high; paraphyses conglutinated, sparingly branched in upper part, c. 1.5 μm thick the apical cells 2-3 μm wide; hypothecium colourless, 20-35 μm high. Asci 100-200-spored, clavate, the apical dome K/I-. Ascospores 1-celled, hyaline, subcylindrical, 4-7 x 1-2 μm. Photobiont chlorococcoid. Spot tests: thallus K-, C+ red, KC+ red, P-. Chemistry: gyrophoric acid.
Note: a mild-temperate, mainly Mediterranean-Atlantic lichen found on steeply inclined, sunny faces of basic siliceous substrata, on roofing tiles and brick. Most common in Tyrrhenian Italy (e.g. on monuments and walls around Rome), below the montane belt.