Distribution: N - Ven, TAA, Lomb, Piem (Isocrono & al. 2004), Lig. C - Tosc, Abr (Nimis & Tretiach 1999), Sar (Scheidegger 1993, Rizzi & al. 2011). S - Si (Scheidegger 1993, Grillo 1998, Grillo & Caniglia 2004).
Description: Thallus crustose, areolate, pale green grey to yellowish grey, not pruinose, sometimes delimited by a black prothallus, forming patches to 5 cm diam. Areoles rather small, 0.2-1 mm wide, flat to convex; medulla white, I-. Apothecia lecideine, 0.3-0.5 mm across, immersed, with a black, flat, not pruinose disc and a thin, externally poorly visible proper margin, sometimes surrounded by a thalline collar. Epithecium brown, N+ red; hymenium 80-120 μm tall, colourless to pale brown, not inspersed; paraphyses simple; hypothecium pale brown to brown, greenish in upper part. Asci 8-spored, clavate, Bacidia-type. Ascospores 1-septate, brown, ellipsoid, thin-walled throughout, (11-)13-17(-21) x 6.5-11.5 μm, finely warted. Pycnidia immersed. Conidia 4-6 x 0.8-1 µm. Photobiont chlorococcoid. Spot tests: thallus K-, C+ persistent orange, P-, UV-. Chemistry: xanthones, especially arthothelin.
Note: a temperate, perhaps holarctic species found on small siliceous pebbles, but also on steeply inclined faces near the ground, below the subalpine belt.