Thallus areolate-cracked, uniform, matt, smooth, areolae angular, minute, 0.15 mm diam., or less, separated by narrow cracks, yellowish-white or yellowish-grey, with distinct, narrow, black, wavy lines at margins and small blackened areas (?prothallus) scattered through thallus, forming coalescing mosaics, 1-5(-8) cm diam., saxicolous. Fertile verrucae scattered to crowded, rounded, ± hemispherical, with a flattened apex, monocarpic, ostiole black, 0.05-0.1 mm diam. Asci clavate, 6-spored (occasionally 4-spored). Hymenial gelatine reddish-brown. Ascospores oval, thick walled, often brownish when young, colourless at maturity (56.5-)74-87 × 34-43.5 µm. Wall 8-12 µm thick. Chemistry: K+ red or brownish. ?Arthothelin, UV+ dull orange.