Thallus 1-8 cm diam., monophyllous occasionally appearing polyphyllous, ± orbicular, attached by central umbilicus, margins free, subascendent, entire or fissured, upper surface undulate, ± finely wrinkled, becoming coarsely reticulate, areolate-cracked at umbo, surface smooth or granular-pruinose in part, dark slate-grey to pale greyish-pink or pale brownish-yellow. Lower surface dark grey to black, wrinkled or plane, rather scabrid, rhizinate. Rhizines in a ± dense nap over lower surface and often at margins, and occasionally projecting through fissures onto upper surface, ± richly branched, pale greyish-brown, thick, often flattened. Apothecia sessile to immersed, 1-3 mm diam., often surrounded by radiating cracks, disc black, plane or subconvex, margins black, prominent, entire, becoming crenulate-convolute with age, central sterile tissue visible as small papillae or fissures. Ascospores colourless, ellipsoid, simple, 11-15 × 6-9 µm.