Tephromela grumosa (Pers.) Hafellner & Cl. Roux

    Thallus crustose, rather thick, 10-12 cm across, markedly cracked in places and areolate, areoles 2-5 mm diam., convex, completely covered with powedery/granular soralia resulting from the breaches in the cortex, indigo-blue, blue, dark blue when young but fading to farinose grey or greenish when old. Apothecia very rare, often absent, disc dark grey to blackish, exciple strongly sorediate and powdery. Photobiont: Chlorococcoid. C-, K+/- yellow, Pd-, UV-. This species has mountainous trends but is commonly found on vertical walls of ancient slate quarries in the Arrée Mounts.*