Protoparmeliopsis muralis var. dubyi (Müll. Arg.) Haffelner & Türk

    Thallus crustose, 5-15 cm across, loosely attached to the substratum, cushion-forming with margin almost foliose-like, lobes flat to slightly convex, apices widened, margin somewhat powdery, whitish, upper surface glossy, pale green-yellowish when dry, celadon-green when moist, lower surface dark brown-blackish. Apothecia usually numerous, crowded, discs paler than the type, grey-yellowish, very pale brownish. Ascospores identical to the type. Photobiont: Trebouxia. Chemical spot tests negative. Rare, montane, calcifuge, saxicolous. Avoid calcareous and nutrient-rich substrata; on schists ridges of the Monts d'Arrée, central Brittany.