Distribution: N - Ven, TAA, VA (Piervittori & Isocrono 1999). C - Tosc (TSB 10470), Sar.
Description: Thallus crustose, episubstratic, rimose-areolate, <0.5 mm thick, smooth, whitish or dirty grey with an ochraceous hue, forming large patches, with or without a dark prothallus. Cortex indistinctly delimited, 35-50 µm thick; medulla white, filled by rock particles, I-; algal layer not extending below the hypothecium. Apothecia lecanorine-aspicilioid, immersed in the areoles, 1-3 per areole, 0.2-0.6 mm across, usually irregular in outline, with a concave to flat, black disc, and a thick but not prominent, dark thalline margin. Epithecium greenish to olive-brownish, N+ emerald green; hymenium colourless, 120-130 µm high, I+ yellowish brown; paraphyses coherent, the apical cells to 3 µm wide; hypothecium colourless, 40-50 µm high. Asci 8-spored, clavate, the thin outer coat K/I+ blue, the wall and apical dome K/I-. Ascospores 1-celled, hyaline, ellipsoid, 18-22 x 10-12 µm. Pycnidia immersed, with a black to brown, punctiform ostiole and a pale wall. Conidia thread-like, 8-12 x c. 1 µm. Photobiont chlorococcoid. Spot tests: cortex and medulla K-, C-, KC-, P-. Chemistry: without lichen substances.
Note: on periodically submerged schistose rocks along brooks in upland areas; most frequent in the Alps. According to Roux & coll. (2014) records from lowland areas are due to confusion with other species.