Thallus areolate, up to 5 cm diam.; hypothallus indistinct, black; areolae up to 0.5 mm diam., medium grey to pale brown, dull, contiguous, orbicular to angular, moderately to strongly convex or verrucose; medulla KI–. – Apothecia up to 0.8 mm diam., black, epruinose, orbicular, persistently plane to slightly convex, with a persistent margin; excipulum brownish black in the rim, inner part paler brown, containing crystals dissolving in K, pigment K–; hypothecium dark brown, K–; hymenium colourless, containing crystals dissolving in K; epihymenium medium brown, K–; ascospores 8 per ascus, eumuriform, persistently colourless, 24–32 × 10–14 µm. – Conidiomata not seen.
Norstictic acid; spot tests: medulla PD+ yellow, K+ red, C–.
On siliceous rock. Rarely collected.
The colourless, muriform ascospores, 8 in the ascus, and the norstictic acid in the medulla (K+ red) are diagnostic.