Mitt. bot. Staatssamml. München, 23: 387, 1987. Basionym: Lecidea lulensis Hellb. - K. svenska Vetensk-Akad. Förhandl., 24: 1863, 1865
Description: Thallus crustose, episubstratic, continuous to areolate, whitish, pale grey or beige, matt to slightly glossy, 0.1-0.2 mm thick, often delimited by a black prothallus, forming small, 0.5-1(-1.5) mm wide patches. Areoles angular, 0.2-0.5(-1) mm wide, flat to slightly convex, contiguous. Medulla white, I+ blue. Apothecia lecideine, 0.2-0.5(-1.5) mm across, dispersed to confluent, adnate or with a slightly constricted base, with a black to brown-black, epruinose, concave to slightly convex disc, and a thin, often finally excluded proper margin. Proper exciple greenish-black to olive-black in outer part, colourless, brownish or pale green within, K+ yellow turning red; epithecium greenish to dark olive-green; hymenium colourless, 60-65 μm high, I+ blue; paraphyses mostly simple, 1.5-1.7 μm thick at mid-level, the apical cells 3-3.5 μm wide; hypothecium colourless. Asci 8-spored, clavate, approaching the Lecanora-type, but with a well-developed, weakly amyloid tholus and a relatively narrow, non-amyloid axial mass. Ascospores 1-celled, hyaline, broadly ellipsoid, (7-)10-12(-15) x (3.5-)4-5.5(-7) μm. Pycnidia black, immersed. Conidia thread-like, curved, 13-23 x c. 0.5 μm. Photobiont chlorococcoid. Spot tests: thallus and especially upper part of medulla K+ yellow turning red (needle-like crystals), C-, KC-, P+ yellow-orange. Chemistry: norstictic acid, sometimes with variable amounts of connorstictic and stictic acids.
Note: on horizontal or weakly inclined faces of siliceous and often iron-rich rocks near and above treeline; with a few scattered records from the Alps outside Italy; to be looked for in the Italian Alps.