Thallus orbicular to spreading, loosely attached, to 10 cm diam., corticolous. Lobes rounded, to 8 mm wide, margins sinuous, brown, moderately ciliate, cilia fine, black, to 4 mm long. Upper surface smooth, matt, pale greenish-grey to whitish, becoming reticulate-cracked centrally, moderately to densely isidiate. Isidia marginal and laminal, small, protuberant, to 1 mm tall, terete, brown-tipped, simple, becoming coralloid-branched and eventually sublobulate, often with small (1 mm), black cilia at base. Lower surface black with a smooth, shining, wrinkled, pale brown, naked marginal zone. Rhizines central, dense, black, simple. Apothecia not seen. Chemistry: Cortex K+ yellow; medulla K+ yellow, C-, KC-, Pd+ orange. Stictic acid and atranorin.