Thallus orbicular to irregularly spreading, loosely attached, large, 5-20 cm diam., corticolous or saxicolous. Lobes rounded, 10-15 mm wide, margins entire, sinuous, often minutely crenate or isidiate. Upper surface whitish-grey, smooth, shining, often maculate (×10 lens), densely isidiate. Isidia mainly simple, rarely coralloid-branched, granular-papillate to coarse, cylindrical, brown-tipped, to 2 mm tall, laminal and marginal. Lower surface black with a broad brown, naked marginal zone. Rhizines central, long, black, simple, rather sparse. Apothecia not seen. Chemistry: Cortex K+ yellow; medulla K-, C+ red, KC+ red, Pd-. Lecanoric acid and atranorin.