Description: Thallus small-foliose to subsquamulose, homoiomerous, gelatinous when wet, 5-10 mm wide, forming rounded cushions. Lobes few, 0.5-1.5 mm wide, flattened, adpressed to erect, usually branched, distinctly swollen. Upper surface dark olive-green to brown or black, dull, epruinose, without isidia; lower surface usually paler. Upper and lower cortices absent. Apothecia crowded, often hiding the lobes, sessile, with constricted base on lobe margins or terminal 0.5-1(-2) mm across; disc plane to convex, dark reddish brown; thalline margin rather thick, eventually disappearing, entire, smooth. Proper exciple euthyplectenchymatous; hymenium colourless, 70-80 µm tall. Asci 8-spored, clavate, the apex thick, with a I+ blue apical dome and a I+ blue annulus projecting downwardly. Ascospores 3-septate, hyaline, ellipsoid with rounded ends, slightly restricted at septa, 14.5-22.5 x 6-8.5 µm. Pycnidia common, immersed, globose. Conidia bacilliform, slightly swollen at the ends. Photobiont cyanobacterial (Nostoc), in long chains. Spot tests: all negative. Chemistry: without lichen substances.
Note: a mild-temperate species found on base-rich bark, especially of Juglans and Populus; more widespread in the past, but locally still common near small settlements in montane valleys, e.g. in the eastern Pre-Alps. It is included in the Italian red list of epiphytic lichens as “Near-threatened” (Nascimbene & al. 2013c).