Distribution: N - Frl, Ven (Nascimbene & al. 2005b), TAA (Nimis & al. 2015). C - Tosc, Marc, Abr (Nimis & Tretiach 1999).
Description: Thallus crustose, greenish or grey-green, minutely granulose, very thin and often indistinct. Apothecia lecideine, 0.2-0.4 mm across, round to sometimes confluent and irregular in outline, yellowish-brown, red-brown to brown-black, with a concave to strongly convex disc and an initially raised, but soon excluded proper margin. Proper exciple pale yellow to dark brown in outer part, more or less colourless within, 40-50 μm thick laterally, K-; epithecium pale brown; hymenium colourless, 40-60 μm high, I+ blue; paraphyses not coherent, more or less branched in upper part; hypothecium pale yellow, 20-30 μm high, K-. Asci 8-spored, clavate, with an an amyloid, slightly broadening tube-structure, approaching the Psora-type. Ascospores 1-septate, with one cell larger than the other, hyaline, ellipsoid (6-)8-15 x 3-5(-6) μm. Photobiont chlorococcoid. Spot tests: thallus and apothecia K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: on hard lignum, e.g. on horizontal faces of old stumps. According to Coppins (1981) the epithet "erysiboides" was used for widely different taxa (e.g. Mycobilimbia carneoalbida, Lecania cyrtella and related taxa, Micarea prasina, etc.); records from Toscana and Marche (Nimis 1993: 204) need confirmation: they could refer to Micarea prasina or related species. The species does not belong to Catillaria s.str.