Thallus usually irregular in outline, lobes not distinctly radiating, 0.5-1.5 mm wide, pale white to whitish grey, often faintly pruinose, not white-flecked, usually appearing ± flattened, with marginal crenulations or horizontal lobules, the apices of which often dissolve into granular soredia; when soredia development is abundant ± lip-shaped soralia may be formed (usually when on rocks). Underside whitish or with faint pinkish, creamy yellow or brownish tinge. Rhizines rather sparse, mostly simple, white to pale brown. Lower cortex pseudoparenchymatous. Anamorph: conidiomata pycnidia, rare. Teleomorph: ascomata apothecia, to 1.5 mm diam., very rare. Ascospores 15-24 × 9-11 (-13) μm. Chemistry: cortex K+ yellow (atranorin), medulla K–.