Thallus corticolous, with several, small, generally erect and fertile branches, and numerous short, crowded, sterile branches at base. Fertile branches to 2.5 cm long and 0.8-1.6 mm wide, subterete to flattened. Upper surface smooth, green-grey to green-grey-yellow, commonly with a few, short, dentate or flattened isidia-like branchlets occurring towards apex, lower surface pale, smooth, or sparsely, irregularly wrinkled, upper cortex 45-70 µm thick, lower cortex 40-60 µm thick. Algal layer 15-30 µm thick, continuous below upper cortex, but occurring rarely or not at all above lower cortex. Apothecia common, subterminal, 1-2 mm diam., mazaedium subterminal, becoming exposed at an early stage of development by irregular apical rupture of enclosing receptacle, prominent, black, globose at maturity. Asci 40-50 × 4.5-6 µm. Ascospores spherical, grey, 5.4-6.8 µm, commonly surrounded by black, carbonaceous material. Chemistry: K-, Pd+ red. Sphaerophorin and protocetraric acid.