Description: Thallus crustose, bright yellow, of rounded, coarse, ecorticate granules or warts forming a more or less continuous crust. Outermost part of granules densely inspersed with minute, yellow crystals. Apothecia frequent, developing from the lower side of granules, stalked and pin-like, 0.6-1.4 mm tall. Stalk 0.04-0.09 mm thick, black to pale brown, with a yellow pruina at least in the upper part. Capitulum obovoid to obconical, 0.15-0.3 mm wide; exciple well developed, with a dense yellowish green pruina on the lower side; hypothecium broadly obconical, with a flat to slightly concave upper surface. Asci cylindrical, 14-19 x 2-3.5 µm, with a 5-9 µm long, narrow stalk, arising singly from ascogenous hyphae with hooks, degenerating early. Ascospores 1-celled, brown, uniseriate, short ellipsoid to globose, (6-)7-9 x 4-5 µm, with a coarse and irregular ornamentation, accumulating at the surface of the ascomata. Conidia 1-celled, 2-3 x c. 1 µm. Photobiont trebouxioid, with isodiametric cells. Spot tests: thallus K-, C-, KC-, P-. Chemistry: apothecial pruina and thallus with vulpinic acid.
Note: a boreal-montane, circumpolar species found on the acid bark of both broad-leaved trees and conifers, more rarely on hard lignum, with optimum on Larix near treeline.