Xanthoparmelia mougeotii (Schaer. ex D. Dietr.) HaleThallus foliose (subcrustose-areolate in central parts), heteromerous, dorsiventral, closely adnate, yellowish green in peripheral parts, greyish in central parts, more or less glossy, forming 0.5-2(-4) cm wide rosettes. Lobes sublinear, elongate, (0.2-)0.5-1(-1.5) mm wide, smooth to rugulose, sometimes transversely cracked with age, epruinose and emaculate, sorediate, the soredia farinose, arramged in orbicular, capitate, 0.5-1 mm wide, yellowish white soralia. Lower surface brownish black, with dark brown to black, simple, 0.1-0.2 mm long rhizines. Upper cortex paraplectenchymatous, with a pored epicortex, the cell walls with <i>Xanthoparmelia</i>-type lichenan; medulla white; lower cortex paraplectenchymatous. Apothecia very rare, lecanorine, with a brown to dark brown disc and a smooth thalline margin. Epithecium brown; hymenium and hypothecium colourless; paraphyses simple; hypothecium colourless. Asci 8-spored, clavate, the K/I+ blue tholus penetrated by a faintly amyloid apical cushion with parallel or diverging flanks, the wall K/I-, surrounded by a K/I+ blue outer layer, <i>Lecanora</i>-type. Ascospores 1-celled, hyaline, broadly ellipsoid, (6-)7-9(-11) x 4-6 µm. Pycnidia rare, laminal immersed, black. Conidia weakly dumbbell-shaped, 4-6 x c. 1 µm. Photobiont chlorococcoid. Spot tests: upper cortex K-, C-, KC+ pale yellow, P-, UV-; medulla and soralia K+ orange, C-, KC+ orange, P+ orange, UV-. Chemistry: upper cortex with usnic acid (major); medulla with stictic acid (major), constictic and norstictic acids (both minor), and traces of cryptostictic and peristictic acids.