Thallus 0.1 mm thick, reddish-brown or olivaceous or dark mottled grey, roughened in parts, minutely areolate, areolae 0.1 mm diam., ± angular to rounded, flat, prothallus black, wavy, marginal, in patches 0.5-5 cm diam., often confluent in mosaics. Apothecia scattered, sessile, rounded, constricted at base, minute, 0.5-0.8 mm diam., disc black, matt or shining smooth or minutely roughened, epruinose, concave at first becoming plane then convex, margin persistent, entire. Hypothecium brown-black. Ascospores biseriate, brown, ellipsoid to oval, apices rounded or slightly pointed, straight, septum thin, 12-15 × 6-7 µm.