Thallus crustose, uniform, spreading, smooth to somewhat unevenverrucose, or with lobulate isidia, greenish-white or pale grey-white, corticolous, muscicolous or rarely saxicolous. Photobiont green, Chlorococcoid. Apothecia sessile to ± pedicellate usually constricted at base, to 4 mm diam., disc yellow or golden, ochraceous to ± blackened, ± pruinose, often contorted with sterile tissue, plane to subconvex, margins thin or thick, yellow, orange, ochraceous or rarely black, entire to crenate or ± inflexed. Asci of -type, without an external apical cap but with thick, I+ blue-staining external wall layer, inner apical apparatus present and inner wall layers amyloid (I+ blue). Ascospores 1, exceptionally 2 per ascus, ellipsoid, colourless, mature spores brownish, muriform, large, to 150 µm long (immature spores may be much smaller). Paraphyses thin, with a few anastomoses and branches, not distinctly thickened at apices. Epithecium and excipulum encrusted with yellowish crystals (K+ red-purple). Thallus K+ yellow (atranorin and chloratranorin).