Thallus inconspicuous, not well delimited, present as a thin layer below the bark surface. Photobiont trentepohlioid. Anamorph: conidiomata pycnidia, frequent, found mostly towards the edge of the thallus, to 40 µm diam., dark brown to black, up to 40 μm diam. Conidia bacilliform, 3–4 × ca 1 μm. Teleomorph: ascomata perithecial, 150–200 (–375) μm diam., spherical to slightly elliptical in outline, dark brown to almost black, glossy, arising singly under an involucrellum, the ostiole central, situated in a small depression. In vertical section dimidiate, the involucrellum 15–20 μm thick, incorporating elements of bark, composed of globose cells around the ostiole, merging into intertwined hyphae towards the sides, reddish to dark brown in water mounts, unchanged in potassium hydroxide, extending a little into the thallus to form a narrow fringe to 40 μm long. Exciple hyaline, to 10 μm thick, consisting of a few layers of isodiametric cells 3–5 μm diam. Interascal tissue consisting of persistent richly branched pseudoparaphyses, 1·5–2·5 μm diam., moniliform, immersed in a gel that is greenish amber in Lugol's iodine. Asci (40–) 55–60 (–85) × 12–18 μm, obpyriform to saccate, fissitunicate, the inner layer narrowing at the apex, not blueing in iodine, mostly 8-spored. Ascospores arranged irregularly, (20–) 25–27 × (4·5–) 5–6·5 μm, cylindric-ellipsoidal, 1-septate, slightly constricted at the septum, the lower cell becoming narrower towards the tip, hyaline but some becoming dark brown and finely warty with age, without an epispore or gelatinous sheath.