Thallus to 5 cm diam., crustose, continuous or partly rimose, white, matt, pruinose. Prothallus usually poorly developed, black, white-pruinose. Upper cortex well-developed. Lower cortex absent. Photobiont chlorococcoid. Anamorph: no information available. Teleomorph: ascomata apothecia, to 1.5 mm diam., mainly orbicular, flat or becoming moderately convex. Disc black, hardly pruinose. Thalline exciple absent. True exciple thick, usually persistent, distinctly pruinose, brown-or green-black at the rim, inner part pale brown to colourless, K+ yellow, with crystals partly dissolving in K. Epithecium olive-brown, with crystals dissolving in K, crystals K+ yellow. Hymenium hyaline, 130-180 μm high, K/I+ blue. Hypothecium dark brown, K–. Interascal tissue of cellular pseudoparaphyses, conglutinate, richly branched and anastomosed, the apical cell slightly thickened. Asci cylindrical, fissitunicate, with a well-developed tholus that is K/I– in the lower part and K/I+ blue near the apex, lacking an ocular chamber, 8-spored. Ascospores 18-28 × 10-16 μm, submuriform, persistently hyaline, smooth, with a broad perispore that degenerates at maturity. Chemistry: medulla K+ yellow, Pd+ orange (stictic acid).