Thallus white or pale grey, occasionally light blue-grey, areoles arising on prothallus when visible, soon coalescing and cracking; ± plane or gently convex between cracks, 100–400 µm thick; very frequently with raised rugose galls caused by Cecidonia xenophana. Prothallus blue-black to black. Anamorph: conidiomata pycnidia, frequent, to 600 µm diam., multilocular, with several ostioles, the apex irregular, black. Conidia 8–11 x ca 1 µm, aseptate, colourless, straight. Teleomorph: ascomata apothecia, to 2 mm diam., becoming sessile as soon as the young disc begins to expand, margin smooth or rarely faintly striate, 60–220 µm wide, eventually ± excluded in old apothecia; disc plane to strongly convex when mature; pruina sometimes present on inner edge of young apothecial margin, present or absent on mature disc. Exciple densely pigmented at surface, brown to dull green-brown or dark dull greenish blue, within paler, brown throughout. Hypothecium brown to red-brown. Hymenium 100–140 µm high. Epihymenium dull green-brown or brown, K–. Interascal tissue of paraphyses, 1.5–2.0 mm diam., the apices 3-3.5 µm diam., the cells colourless or dilute brown, surrounded by pigment (epihymenial pigment mostly extracellular). Asci clavate, 8-spored, tholus with an I+ blue tube structure. Ascospores (15.0–) 16.5–20.5 (–21.5) x (7.5–) 8.0–10.5 (–12.5) µm, ellipsoidal, aseptate, colourless, with a gelatinous sheath. Chemistry: thallus K–, PD–, C– ; microscopic preparations in K not exuding minute droplets.