Thallus dorsiventral, heteromerous, foliose-lobate, orbicular to spreading, often very large, loosely to closely attached, corticolous or saxicolous. Lobes broad, rounded, 10-30 mm wide, margins entire or variously incised or ornamented, ± ciliate. Upper surface smooth, shining or dull, plane, undulate or wrinkled, with or without, isidia, maculae, soredia. Upper cortex of palisade plectenchyma with a well-developed, pored epicortex. Medulla white. Photobiont green, . Lower surface black, with a characteristic brown or pale, marginal zone free of rhizines. Rhizines simple, unbranched, rather sparse, often coarse, central. Apothecia pedicellate, disc often perforate, thalline exciple smooth to wrinkled, sometimes maculate. Ascospores simple, colourless.