Thallus, dorsiventral, heteromerous, foliose-lobate, mono- or polyphyllous, attached to substrate by central umbilicus, soft, pliable and somewhat leathery when wet, brittle when dry. Upper surface partially or weakly ribbed or folded or reticulate-ridged, to smooth, continuous, areolate-cracked to ± perforate or lacerate, margins sinuous, entire to ragged or incised, rhizinate or not. Lower surface black or pale brownish or pinkish, smooth, or bullate or wrinkled- uneven, rhizinate or not. Medulla white. Photobiont green, . Apothecia sessile to pedicellate, lecideine, discrete, plane to convex, disc black, plane, smooth or with conspicuous ridges (gyrae) or bands of sterile tissue. Ascospores 8 per ascus, simple, ellipsoid, colourless, becoming brown and muriform in some species.