Thallus to 6 cm diam., foliose, forming rosettes or irregularly spreading, dark brown to black, grey-black, rarely dark olive, closely appressed, attached to substratum by irregular, peg-like, cortical outgrowths. Rhizines absent. Lobes 0.2-1 mm wide, convex, dorsiventrally flattened, elongate, somewhat gnarled, contiguous, often overlapping and entangled, particularly in older parts, at times so tightly compacted as to appear crustose towards the centre; corticate on both sides. Upper surface without pseudocyphellae, soredia or isidia. Lower surface black, ± pleated. Cortex hyphal in structure, arising from hyphae perpendicular to surface, K–, N–; upper and lower cortex similar in structure. Photobiont chlorococcoid. Anamorph: conidiomata pycnidia, ± immersed in thallus. Conidia 4.5-6 × 1 μm, colourless, bifusiform to bacilliform or slightly clavate. Teleomorph: ascomata apothecia, to 5 mm diam., laminal, sessile, disc brown-black; margin entire, rarely crenate. Thalline exciple present. Hymenium colourless. Asci 8-spored, Lecanora-type. Ascospores 7.5-10 × 5-7 μm, colourless, ellipsoidal to globose, aseptate. Chemistry: medulla C+ rose-red, K+ yellow, KC+ red, Pd+ bright yellow, UV– (alectorialic and barbatolic acids).