Distribution: N - TAA, Piem (TSB 34606), VA (Piervittori & Isocrono 1999).
Description: Thallus minutely squamulose, growing in very fine cracks of calciferous rocks. Squamules adpressed, scattered, 1-5 mm wide, finally deeply lobed, c. 500 μm thick, smooth, epruinose, pale to medium brown, paler at margins, the lower surface dirty white, attached by bundles of rhizines. Apothecia almost always present, lecideine, reddish brown to almost black, often crowded, sessile, to 1.5 mm across, at first with a flat disc and a prominent margin, finally convex, epruinose. Cortex overlain by a epinecral layer; medulla white, I-. Proper exciple and hypothecium thick, medium to dark brown, of conglutinated hyphae; epithecium brown; hymenium colourless, c. 65 μm high; paraphyses conglutinated, 2-2.5 μm thick, slightly swollen and brown at apex; hypothecium and lower part of hymenium with blue-black granules reacting K+ green. Asci 8-spored, clavate, with a I+ blue tholus and an internal, darker I+ tubular structure, the external gel I+ faintly blue, Porpidia-type. Ascospores 1-celled to sometimes finally 1-septate, hyaline, ellipsoid to narrowly ellipsoid, 10-15.5(-18) x 4-4.5 μm. Photobiont chlorococcoid. Spot tests; thallus and medulla K-, C-, KC-, P-, UV-. Chemistry: thallus apparently without lichen substances.
Note: a probably circumpolar, arctic-alpine lichen found in thin fissures of calciferous rocks (calcareous schist, dolomite, much more rarely pure limestone) near and especially above treeline; certainly more widespread in the Alps.