Distribution: N - VG (Tretiach 1993), Ven (Lazzarin 2000b), TAA, Lomb, Piem (Isocrono & al. 2004), Lig (S-F145460). C - Marc (TSB 33889), Abr (Jatta 1909-1911). S - Camp (Nimis & Tretiach 2004, Garofalo & al. 2010), Pugl, Si (Nimis & al. 1994, 1996b).
Description: Thallus squamulose, homoiomerous, slightly gelatinous when wet, in section with a loosely reticulate network of thin hyphae enclosing groups of cyanobacterial cells. Squamules 1-2 mm wide, brown-black to black, but usually blue-pruinose, with a mostly entire margin, dispersed to usually crowded and forming effuse crusts, with an entire to shallowly incised margin, covered in small, soredia- or isidia-like granules. Apothecia pycnoascocarps, 1-2 per squamule, at first immersed and urceolate, but soon expanded and clearly lecanorine, 0.3-0.5 mm across, with a dark reddish brown, concave to flat disc, and a thick, rugose, pruinose thalline margin. Proper exciple absent or very thin, cupular; epithecium orange-brown, thin; hymenium colourless, 100-150 µm high, the hymenial gel I+ deep blue; paraphyses in part simple, straight, long-celled, partly moniliform, 3-4 µm thick, the apical cell slightly swollen, up to 5 µm wide; hypothecium pale orange-brown, 20-50 µm high in central part. Asci 8-spored, cylindrical-clavate, thin-walled, with an amyloid external apical cap. Ascospores 1-celled, hyaline, broadly ellipsoid to subglobose, 9-15 x 7-10 µm, the wall 1-2 µm thick. Pycnidia immersed, globose to pyriform, unilocular or secundarily plurilocular, 70-140 µm wide. Conidia hyaline, ellipsoid to narrowly ellipsoid, 2.5-4 x 1.5-2 µm. Photobiont cyanobacterial, chroococcoid, of a few. 3-5 µm wide cells often penetrated by haustoria and surrounded by a gelatinous sheath which is colourless in inner parts, yellowish brown near the thallus surface. Spot tests: all negative. Chemistry: without lichen substances.
Note: on steeply inclined, sunny surfaces of calcareous rocks (mainly limestone, but also calciferous schists and sandstone) with periodical water seepage after rain, below the subalpine belt. Probably widespread throughout the country.