Thallus usually rounded or fan-shaped in outline, rarely irregular, 1–5 cm diam., sometimes aggregated in compound structures 10–20 cm diam. with several thalli intermingled and overlapping each other; subcoriaceous, brittle when dry, branching mostly dichotomous with 1–3(−5) ramifications per main lobe; stipe absent. Lobe branches slightly ascending, typically involute and forming slightly concave fan-shaped forms, 4-8 mm wide, laciniate, often slightly tongue-shaped, with rounded to irregular tips, the margins sometimes slightly swollen, rarely dissected or irregularly lacerate. Upper surface usually dark brown when wet, paler and sometimes bluish grey when dry, usually glossy, typically foveolate or scrobiculate with shallowly reticulate ridges, not maculate. Cilia usually absent, but frequently detected between the main lobes, where they are scattered and mimic the tomentum, simple, white to pale, less than 0.5 mm long. Isidia always present, developing mainly on lobe margins or on ridges of the upper surface, sometimes covering large parts of the thallus, globulose and developing coralloid masses to 500 µm high and diam., very brittle and easily detached from the thallus, dark brown to almost black. Lower surface uneven or slightly foveolate, brown to dark brown to almost black; tomentum sometimes absent on the edges of lobes but most usually abundant throughout, forming a spongious mat when well-developed. Cyphellae always present on the lower surface, usually dispersed, rounded or slightly irregular, 800-1100 µm in diam., erumpent and slighlty involute, the outer wall sometimes brown, the pore 500-700 µm diam., the surface cells sometimes papillate. Photobiont Nostoc. Anamorph and teleomorph: not known.