Description: Thallus crustose, episubstratic, rimose-areolate to warted, ecorticate, yellowish, yellowish green, more rarely greenish grey, without a distinct prothallus, the areoles irregular in outline, 0.15-0.3(-0.5) mm wide, weakly convex. Apothecia lecanorine, round to irregular in outline, sessile and constricted at base, 0.5-1.5 mm across, urceolate when young, with a yellowish green to orange-brown, flat, dull, white-pruinose disc, and a prominent, often inrolled, sinuose, persistent thalline margin. Thalline exciple corticate, the cortex 25-80 µm thick laterally, 90-150 µm near base, the hyphae with 1.5-2.5 µm wide lumina, the medullary part rich in algae; epithecium colourless to pale brown, 6-13 µm high, with many small yellow-brown granules soluble in K; hymenium colourless, 50-90 µm high; paraphyses simple or sparingly branched and anastomosing, 1.5-2 µm thick at mid-level, the apical cells hardly swollen; hypothecium colourless in upper part, pale yellow in lower part, 30-40 µm high. Asci 8-spored, clavate, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid, 10-12.5 x 4-5.5 µm. Conidia thread-like, often curved, 12-22 µm long. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC- or KC+ pale yellow, P+ bright yellow, UV+ dull orange. Chemistry:usnic, psoromic and 29-O-demethylpsoromic acids, sometimes with additional diffractaic acid.
Note: a cool-temperate to circumboreal-montane lichen found on hard lignum, more rarely on smooth, hard, acid bark, especially of conifers, in upland areas; most frequent in the Alps, but also occurring in the Mediterranean mountains.