Gams ex Coppins, Checklist Lich. Great Brit. Ireland: 86, 2002. Basionym: Biatora micrococca Körb. - Parerga Lichenol.: 155, 1860.
Synonyms: Lecidea micrococca (Körb.) Cromb.
Distribution: N - Ven (Thor & Nascimbene 2007), Lomb (Herb. Nascimbene 1773). C - Abr (Herb. Nascimbene 2424). S - Cal (CLU 12878).
Description: Thallus crustose, episubstratic, effuse, continuous, pale to dark grey-green, subgelatinous when wet, composed of small, scattered or aggregated, ecorticate, 12-50 µm wide goniocysts, often with protruding hyphae reacting K+ violet. Apothecia micareoid, whitish grey to cream-coloured, sessile, 0.1-0.4 mm across, with a strongly convex, sometimes tuberculate, epruinose disc, without a proper margin. Proper exciple poorly developed, usually indistinct; epithecium colourless or greenish and K+ violet; hymenium colourless, 25-50 µm high; paraphyses numerous, branched, 0.5-1.2 µm thick, not capitate; hypothecium colourless, 40-170 µm high. Asci 8-spored, cylindrical-clavate, the I+ blue tholus with a wide, I+ dark blue tube structure that expands towards the top, without a pale axial body Ascospores (0-)1(-2)-septate, often constricted at septa, hyaline, ellipsoid or oblong-ovoid, 10-12(-16) x 3-4.5 µm. Pycnidia frequent, white or grey around the ostiole, K+ and C+ more or less violet, of 2 types: a) mesopycnidia 50-150 µm wide, globose or barrel-shaped, with a wide ostiole, producing cylindrical to obpyriform mesoconidia measuring 4.5-5.5 x 1.2-1.5 µm; b) micropycnidia 30-60 µm wide, globose, producing bacilliform or narrowly fusiform microconidia measuring 5-8 x 0.8-1 µm. Photobiont micareoid, the cells 4-7 μm wide. Spot tests: thallus and apothecia K-, C-, KC-, P-, UV-. Chemistry: methoxymicareic acid.
Note: a member of the M. prasina-complex, mainly growing on bark or wood, more rarely on soil, plant debris and pebbles; earlier records might be under M. prasina.