Thallus heteromerous, crustose, uniform or effigurate or squamulose and small-foliose, seldom dwarf-fruticose, attached to substrate by hyphae of prothallus or of medulla, rhizines absent, corticate or decorticate. Photobiont green, and possibly other genera. Apothecia sessile, circular, with a well-developed thalline margin, at least when young, in some species excluded at maturity. Paraphyses unbranched, free. Hypothecium colourless or coloured. Asci 8-spored, rarely 16- to 32- spored. Ascospores colourless, ellipsoid, simple, elongate to spherical, rarely spuriously 1-septate, thin-walled. Pycnidia immersed. Conidia bacillar, cylindrical or filiform, straight or curved.