Bryostigma lapidicola (Taylor) S.Y. Kondr. & J.S. Hur

    Thallus crustose very thin and barely visible, often fragmented and reduced to granules or warts, greyish, greenish, yellowish green, olive, brownish,... Apothecia generally numerous, arthonioid, convex to globose with a slightly flattened apex, 0.1-0.3 mm in diameter, not pruinose, black. Ascospores ovoid, 1-septate with one cell larger than the other, 8-12 (14) x 3-4 (5) µm. Pycnidia rare. Photobiont: chlorococcoid. No characteristic colour reactions. Pioneer species, fairly common but neglected, ruderal, growing on all sorts of supports in dirty and polluted areas: mosses, bark, posts, rocks, plastic materials, especially shipwrecks, etc.

Beware of 2 very (too?) similar species:

_ Arthonia fusca ((A. Massal.) Hepp perhaps conspecific.

_ Arthonia apatetica (A. Massal.) Th. Fr. corticolous species with less thick hymenium.