Thallus laciniate, loosely attached, orbicular to spreading 2-8(-15) cm diam., corticolous. Lobes convex, narrow, 0.5-2.0 mm wide, rather short, irregularly to subdichotomously branched, margins entire, apices rounded. Upper surface bright green when wet, pale greenish-grey when dry, smooth, matt or shining, maculate (×10 lens), isidiate centrally, white-pruinose at margins. Isidia simple, finger-like becoming coralloid-branched, laminal, rarely marginal. Lower cortex absent. Hypothallus conspicuous, black, densely compacted, 0.5-1.5 mm thick, continuous over lower surface. Rhizines stout, black, simple, with an anchoring apical tuft. Apothecia and pycnidia not seen. Chemistry: Cortex K+ yellow; medulla K-, C+ red or -, Pd+ red or -. Two chemodemes are found in New Zealand populations, a C+ red, Pd- chemodeme containing anziaic acid and atranorin, and a C-, Pd+ red chemodeme containing fumarprotocetraric acid and atranorin.