Life habit: lichenized, not lichenicolous Thallus: squamulose, attached by basal end of squamule when young, later by a well developed stipe squamules: more or less dispersed when young, later becoming closely appressed, up to 5 mm wide, pulvinate, rounded, lacking vegetative dispersal units upper surface: partly olivaceous brown and shiny in ± concave areas, partly pale gray and dull in ± convex areas, epruinose; margin: pale gray, dull, often slightly raised in young squamules, later indistinct as the squamules become pulvinate and conglomerate upper cortex: scleroplectenchymateous, composed of thick-walled, conglutinated hyphae with thread-like lumina, with cones or strands extending deep into the medulla and often merging with the stipe or lower cortex, covered by a thin epinecral layer, containing brown pigment and crystals dissolving in K in the uppermost 50-100 µm, not containing remnants of algae (chlor-zinc-iodine!) medulla: plectenchymatous, composed of rather thin-walled, only weakly conglutinated hyphae with thread-like lumina, filled with crystals dissolving in K and with remnants of algae (chlor-zinc-iodine!), I- algal layer: in pockets below and between the upper cortex, approaching the upper surface below the gray, dull surface areas photobiont: primary one a chlorococcoid alga; secondary photobiont absent; algal cells: 10-12 µm diam. lower cortex: hardly differentiated from the upper cortex and continuous with this and the stipe lower surface: pale gray to medium brown Ascomata: apothecial, laminal, sessile, not or only slightly constricted at base, up to 1.5 mm diam., black, shiny, epruinose, simple or a few agglomerated, plane to moderately convex, with a narrow and often disappearing margin; exciple: annular, olivaceous green in the rim, colorless in inner part, composed of rather thick-walled, conglutinated, radiating hyphae with shortly cylindrical lumina, containing crystals dissolving in K; epithecium: olivaceous green, containing crystals dissolving in K-; hymenium: hyaline, I+ blue, 50-60 µm high; paraphyses: straight, sparingly branched and anastomosing, moderately conglutinated, apical cell not or only slightly swollen; hypothecium: colorless, composed of thick-walled, strongly conglutinated hyphae with thread-like lumina, lacking crystals, I+ blue, containing algae in the lower and lateral part asci: broadly clavate, with a well developed, amyloid tholus containing an ocular chamber and a broad axial mass (Lecanora-type), 8-spored ascospores: colorless, simple or 1-septate, narrowly ellipsoid, smooth, without halo, 9-15 x 4-6 µm Conidiomata: pycnidial, laminal, immersed in the algal layer and medulla, with a dark green to black ostiole conidia: acrogenous, filiform, straight to curved, 12-20 x c. 1 µm Spot tests: upper cortex K+ yellow, C-, KC-, P+ yellow; medulla K+ yellow turning red, C-, KC-, P+ orange Secondary metabolites: atranorin and norstictic acid. Substrate and ecology: on exposed volcanic rock in the alpine zones, at 3530 - 3720 m alt. World distribution: alpine zones of Europe and North America Sonoran distribution: rare in northern and central Arizona (San Francisco Peaks and White Mountains). Notes: Two chemical strains occur in Europe: atranorin and either norstictic or stictic acid (plus related compounds).