Description: Thallus crustose, endosubstratic, brownish or not evident, not lichenized. Perithecia black, 0.1-0.2 mm across, circular in outline, with a slightly flattened apical part. Involucrellum dimidiate, brown, K-, of thick-walled hyphae; exciple colourless throughout; paraphysoids soon gelatinized, not evident in mature perithecia. Asci 8-spored, obpyriform, thick-walled and fissitunicate, 45-45 x 18-20 μm. Ascospores 1-septate, not constricted at septum, the two cells often of slightly different size, withour a median constriction, hyaline, almost bacilliform, 18-22 x 2.5-3(-4) μm, with a narrow gelatinous sheath. Pycnidia rare, black. Conidia 1-celled, narrowly ellipsoid or bacilliform, 3-4 x c. 1 μm. Photobiont absent. Spot tests: all negative. Chemistry: without lichen substances.
Note: on the smooth bark of deciduous trees, widespread throughout Europe but rarely collected, most records being historical.