Description: Thallus crustose, mostly endosubstratic, olive-brown to dark brown, continuous or weakly rimose. Perithecia black, 0.2-0.3 mm across, immersed only at the base, otherwise projecting, conical. Involucrellum black, not extending below the perithecum; exciple prosoplectenchymatous, at first colourless, then turning blackish, largely fused with the involucrellum, hamathecium of thread-like, 1.5-2 μm thick paraphysoids which are mostly simple, and only rarely branched and anastomosing, except where adjacent to the exciple. Asci 8-spored, narrowly clavate, bitunicate-fissitunicate, shortly stalked at base, the apex thickened into a tholus, with a narrow ocular chamber, non-amyloid. Ascospores 1-septate and strongly constricted at septum, hyaline, fusiform, (16-)19-24(-27) x (3.5-)4-5 μm, separating into part-spores, the latter (8.5-)9.5-12.5(-14.5) x (3-)3.5-5(-5.5) μm. Macropycnidia black, hemispherical, 0.05-0.12 mm across, with an involucrellum. Macroconidia (0-)1-septate, oblong-cylindrical, (12.5-)13.5-17.5(-20) x (2-)2.5-3(-3.5) μm, with a poorly visible (1.5-4.5 x 1-2 μm) gelatinous appendage at each end, each cell with 2–5 oil droplets. Micropycnidia similar but smaller, 0.05-0.1 mm across. Microconidia fusiform or subfusiform, 2.5-4 x 1-1.5 μm. Photobiont trentepohlioid. Spot tests: thallus K-, C-, KC-, P-. Chemistry: thallus without lichen substances.
Note: an often overlooked species found on the bark of broad-leaved deciduous trees (especially Quercus, Alnus, Fraxinus, Juglans) in humid-shaded situations, rarely also on limestone; widespread in Mediterranean and especially Atlantic Europe, and also known from Macaronesia, with several records from the Western Alps (France); to be looked for in Italy