Pertusaria mammosa  Harm.

    Thallus crustose, 1-3 mm thick, grey-olive, ground-grey, markedly verrucose, warts apart, convex, with a whitish soralia on uppermost part (suggesting white spots on a dark background), prothallus more or less visible, sometimes zonate, bulging in case of mosaics. Apothecia very scarce, ontop of fruiting warts, disc dark grey to blackish. Ascii 1-spored. Ascospores 180-200 x 60-70 µm. Photobiont: clorococcoid. Thallus: C-, K+ faint yellow, KC+ brown reddish; medulla and soralia: C-, K+ dull faint yellow, KC+ brown-reddish, Pd+ red. Saxicolous, rare, on more or less vertical siliceous rocks in Mediterranean region, sub-oceanic to littoral, mainly found near the seashore or in areas subjected to humid maritime influence.