Thallus effuse or delimited, sometimes mosaic-forming, evanescent or thin, smooth or rimose to verrucose-areolate, with areoles 100-400 µm diam., beige to more usually dark olivaceous to grey-black or dark grey-brown, matt or slightly glossy. Prothallus black, limiting. Photobiont Myrmaecia, with cells 7-17 μm diam. Anamorph: conidiomata pycnidia, 50-100 μm diam., the wall dark green, the outer cells with dark brown caps. Conidia 1.8-3.5 × 0.5-0.8 μm. Teleomorph: ascomata apothecia, (0.15-) 0.2-0.5 (-1) mm diam., scattered or a few clustered, mostly flat, sometimes becoming convex,
black (rarely dark brown). Proper margin thin, slightly raised, usually concolorous with the disc but sometimes paler. True exciple green-black throughout. Epithecium dark brown to green-black. Hymenium 40-60 μm tall, hyaline or more usually pale blue-green (at least in the lower part). Hypothecium dark brown, K–. Green pigment in epithecium, hymenium and proper margin K– (or green intensifying), N+ purple-red. Interascal tissue of rather thick-walled paraphyses 1.5-2 μm diam., simple or rarely forked, the apices capitate and sometimes moniliform, to 6 μm diam., with a conspicuous dark brown to black cap. Asci subcylindrical to clavate, with a blue outer coat and uniformly blue apical dome in K/I, 8-spored. Ascospores (7.5-) 9-12 (-15) × 2.5-4 μm, ± cylindrical to ovoid-ellipsoidal, constricted at the single ± median septum, hyaline, fairly thin-walled, smooth, sometimes with a narrow gelatinous sheath. Chemistry: lichen products not detected by TLC.