Thallus crustose, effuse, smooth, the surface becoming cracked, often slightly verruculose or areolate. Surface plane to slightly rugose-verruculose, epruinose, grey-brown creamy, 0.1–1.5 mm thick. Cortex 30–60 mm thick. Medulla chalklike but with loose hyphae near the substratum, white. Soralia (usually in the absence of ascomata) punctiform to maculate. Photobiont Trentepohlia. Anamorph: no information available. Teleomorph: ascomata sometimes present (usually in the absence of soralia), numerous, 0.1-2 mm diam., containing multiple locules, discoid, sessile, circular in outline, the base constricted. Disc pruina with finely rimose surface, white-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 18- (21-24) x 5–6 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+ faintly red; medulla C--; disc C+ red. Secondary metabolites: erythrin; lecanoric acid; unidentified substances C, G occasional.