Ochrolechia arborea  

Thallus thin, white to pale grey, often immersed in the substratum, smooth, shiny, little cracked, with a fibrous surface texture, like art paper. Soralia crater-like, with a thin margin, discrete, <0.4 mm diam., circular, becoming convex and efflorescent. Soredia 40-50 μm wide, spherical, dull, pale yellow, to green-grey.
Anamorph: not known.
Teleomorph: not known.
Chemistry: Soralia C+ red, KC+ red, Pd–, UV+ bright orange (gyrophoric acid, lecanoric acid (trace), lichexanthone).