Opegrapha opaca Nyl.

Ascomata lirellate, black, unbranched, almost rounded to elliptical, (150–)200–280(–300) μm diam. (n=10), plain to slightly convex, aggregating to gall-like strongly convex clusters up to 1–1.2 mm diam. Exciple 20–25 µm thick in the lateral part of the ascomata, dark brown in water, K−. Interascal filaments composed of thick-walled paraphyses 2–2.5 µm diam., irregular and sparingly branched in the upper part. Asci 4–6-spored, clavate, (65.0–)70.0–83.4(–92.0) × (12.6–)14.0–16.2(–18.8) μm (n=10). Ascospore 3-septate, hyaline to pale brown when mature, ellipsoid, the ends rounded, slightly constricted at the septa, smooth, with distinct gelatinous sheath up to 2 μm in young ascospores, (15.0–)15.4–17.4(–18.0) × (4.6–)5.0–6.2(–7.0) μm (n=20) (measured only brown ascospores), length/width ratio (2.2–)2.5–3.3(–3.5).