Description: Thallus foliose, gelatinous when wet, loosely attached, isidiate, blue-grey to lead-grey when dry, dark green-grey when wet, 3-5 cm wide. Lobes poorly differentiated, markedly wrinkled and radially ridged, sometimes fenestrate, with dark grey to brown-black (darker than thallus), granular to subcylindrical isidia developing along the margins and on the ridges, finally spreading through the entire surface; lower surface paler, without tomentum. Upper and lower cortices paraplectenchymatous, composed of a single layer of angular cells. Apothecia very rare, lecanorine, substipitate, with a brown disc and an isidiate thalline margin. Epithecium brown to pale orange; hymenium colourless; paraphyses mostly simple, 1-2 µm wide the apical cells slightly swollen; hypothecium paraplectenchymatous, yellowish to pale brown. Asci 8-spored, cylindrical-clavate, the apex thick, with a I+ blue apical dome and a I+ blue annulus projecting downwardly. Ascospores (5-)6-10-septate, hyaline, acicular, 55-70 x 5-6 μm. Photobiont cyanobacterial (Nostoc), in long chains. Spot tests: all negative. Chemistry: without lichen substances.
Note: a mild-temperate to humid subtropical, typically western-Tyrrhenian species in Italy, most frequent in open, humid woodlands, especially in old coastal plantations of Olea.