Thallus crustose, effuse, smooth, the surface becoming cracked, often slightly verruculose or areolate. Surface plane, rugose-verruculose to nearly squamulose or suffruticose, pruinose, white-grey, 0.2–3.5 mm thick. Cortex 40–70 µm thick. Medulla chalklike throughout, white. Soralia (usually in the absence of ascomata) punctiform to maculate. Photobiont Trentepohlia. Anamorph: conidiomata pycnidia, sometimes present, evenly dispersed over the thallus surface, often with a preference for the margins or the immediate margin, immersed or slightly elevated like black or dark brown dots. Conidia 12-16 x ca 1 µm, filiform and sickle-shaped. Teleomorph: ascomata sometimes present (usually in the absence of soralia), numerous, 0.5-3 mm diam., containing multiple locules, discoid, sessile, circular in outline, the base constricted. Disc pruina with rimose surface, white-grey to dark grey. Thalline margin present, entire to undulating and often strongly so. Hypothecium carbonaceous or dark brown, usually sharply defined towards the white medulla. Hymenium hyaline, 50-140 µm thick. Epithecium brownish, 35–80 µm thick. Interascal tissue of pseudoparaphyses, branched and intertwined, with smooth or slightly ornamented tips 1–3 µm diam.; incorporated crystals often make the separate hyphae hard to distinguish. Asci clavate, fissi- or semifissitunicate, 8-spored. Ascospores 20-24 x 4–6 µm, fusiform or obtusely fusiform, often curved, often with one end tapering more than the other, 3-septate, hyaline and smooth, when old sometimes brownish, gelatinous sheath absent or inconspicuous. Chemistry: thallus surface C+ red; medulla C--; disc C+ faintly red. Secondary metabolites: erythrin; lecanoric acid; unidentified substances C, D, E H rare.