Thallus 10-20 cm diam., rather thick (to ca 1.5 mm). Lobes 10-20 (-30) mm wide and 100 mm long, often imbricate, deeply incised, the margins ± raised, undulate and sometimes inrolled. Upper surface ± even, downy or greasy, brown tinged blue-green when dry, deep blueish olive-green or brown when wet, smooth or often thinly scabrid-tomentose with erect hairs especially towards the lobe margins, usually glabrescent in the central part. Lower surface ± white to pale brown at the margins, becoming brown-black towards the centre, ± uniformly tomentose, veins and paler interstices few and diffuse or absent. Rhizines to 3mm long, sparse, black, bushy or fasciculate, sometimes entirely absent. Photobiont cyanobacteria (Nostoc). Anamorph: unknown. Teleomorph: ascomata apothecia, rarely developed, on short thalline stalks, 4-8 mm diam., sessile, ± circular, brown-red to dark brown, shallowly convex, ± crenulate at the margin. Ascospores (45-) 55-70 (-90) × (2.5-) 4-6 μm, 3- to 5-septate, elongate-fusiform. Chemistry: thallus with tenuiorin, methyl gyrophorate, ± gyrophoric acid (C+ red) and unidentified terpenoids (as those found in P. leucophlebia).