Bacidia viridifarinosa Coppins & P. James

    Thallus crustose, very thin, 3-8 cm across, minutely granular, grey-greenish, greenish, soon covered with clustered soredia, forming irregular confluent bright green-yellow patches, prothallus delimited, arachnean, whitish. Apothecia rare and most often absent, developed mainly in zones devoid of soredia, sessile, circular, 0.4-0.6 mm diam., disc flat to slightly convex, beige-pink at first turning pale brown to dark brown when old, exciple inconspicuous and soon vanishing, darker. Pycnidia immersed in the thallus, visible as minute white dots, 0.15-0.25 mm diam.. Photobiont: chlorophycean. C-, K-, KC-, Pd-, UV+ orange. In our prospection area, rare, oceanic trends, on shaded  smooth and not too acid rocks of oceanic humid woodlands, sometimes on smooth bark at the base of old deciduous trees, notably Quercus. See Bacidia adastra of which the thallus is granular but without confluent soredia and the prothallus brownish. See also Bacidia carneoglauca which has larger white cottony pycnidia (and which might be its fertile form) and Bacidia trachona without soredia.*