Thallus medium to large, foliose, 12-24 cm diam., corticolous, rarely saxicolous. Lobes rounded, 5-10 mm wide. Upper surface pale greenish-grey or ashy white, the margins ± ascendent and commonly isidiate, tips white-pruinose, pseudocyphellae small, punctiform to irregular, rarely more than 1 mm broad, often associated with small, granular or delicately coralloid isidia. Lower surface black, the margins greyish like the upper surface, or brown. Rhizines small, black. Apothecia not seen in New Zealand material. Chemistry: Thallus K+ yellow; medulla K-, C-, KC+ pink, Pd-. Alectoronic and α-collatolic acids and atranorin.