Thallus corticolous, subimbricate, horizontal or decumbent, fertile branches distinctly flattened, irregularly branched, to 5 cm long and 2-5(-8) mm wide, sterile basal branches shorter, flattened, sparsely branching. Upper surface grey- green, smooth, becoming wrinkled and transversely annulate-cracked, in older, larger branches convex, margins thickened, rolled under, plane near apothecia, lower surface concave to ± plane, pale, smooth to irregularly wrinkled, becoming lacunose near apothecia, upper cortex 60-100 µm thick, lower cortex 20-40 µm thick. Algal layer 20-40 µm thick, continuous beneath upper cortex, rarely onlower side. Apothecia common, subterminal 1.5-4(-7) mm diam., mazaedium ventral, exposed at an early stage, at maturity partially enclosed by receptacle, black or covered with a fine greyish dust. Asci 50-65 × 5-8 µm. Ascospores spherical (10-)12-15(-16) µm. Chemistry: Sphaerophorin.