Hypotrachyna revoluta (Flörke) HaleThallus foliose, heteromerous, dorsiventral, rather loosely attached, forming 1-4(-6) cm wide (rarely wider, up to 10 cm), more or less irregular rosettes, sorediate. Lobes irregularly subdichotomously branched with rounded to angular axils, (1-)2-6 mm wide, often imbricate, at first closely adpressed, then slightly ascending at tips, with subtruncate to rounded, often revolute apices (especially when sorediate). Upper surface grey to greenish grey, often with a brownish hue in central parts, dull, emaculate, smooth, with initially subcapitate, subterminal soralia that later coalesce, especially at the revoluted lobe tips, bearing farinose to rarely granulose, whitish to greenish soredia. Lower surface black in central parts, brown in marginal and apical parts, that of young lobes dull, with brown to black, dull, short, forked or sparingly dichotomously branched, rarely simple rhizines, which rarely can project beyond lobe margins snd often are lacking below the sorediate parts. Upper cortex of tightly packed, anticlinally oriented hyphae, with a pored epicortex, the cell walls with isolichenan; medulla white; algal layer continuous; lower cortex brown, of anticlinally oriented hyphae. Apothecia very rare, lecanorine, subpedicellate, 2-6 mm across, with a brown disc and a sorediate thalline margin. Epithecium brownish; hymenium and hypothecium colourless. Asci 8-spored, clavate, <i>Lecanora</i>-type. Ascospores 1-celled, hyaline, ellipsoid, 10-15 × 5-9 μm. Pycnidia black, laminal, immersed. Conidia bifusiform, 4-5 x c. 1 µm. Photobiont chlorococcoid. Spot tests: upper cortex K+ yellow, C-, KC-, P- or P+ faintly yellow; medulla K-, C+ pink, KC+ pink-red, P-, UV-. Chemistry: upper cortex with atranorin and chloroatranorin; medulla with gyrophoric acid (major), 4,5-di-O-methylhiascic acid, 5-O-methylhiascic acid (minor), rarely with traces of lecanoric and umbilicaric acids. 