Thallus monophyllous, often deeply indented and appearing polyphyllous, attached by a single rather deformed umbilicus, 2-8(-12) cm diam., corticolous, occasionally saxicolous. Lobes undulate, folded or ± free, margins entire. Upper surface ± shallowly faveolate-wrinkled or pitted, dark brown-grey or bluish- brown when wet, sometimes ± blackened, pale bluish-grey when dry, often also with white maculae (×10 lens), isidiate. Isidia scattered, terete, simple or coralloid, often ± delicately stalked, very delicate and friable, sometimes in clusters. Lower surface ± uniformly tomentose, pale brown at margins, darker centrally. Cyphellae large, white, round to irregular, 1-2 mm diam. Apothecia not seen.