The
thallus is , meaning it grows embedded within the rock rather than on its surface. The fruiting bodies (
apothecia) are in form (with a rim formed by fungal tissue rather than thallus tissue) and typically numerous, unstalked (), and circular, measuring about 0.25–0.75 mm wide and 0.25–0.38 mm thick. The is black, flat to convex, roughened, and lightly frosted (slightly pruinose). The outer rim () is dark brown and about 62.5 μm thick, the uppermost layer of the spore-bearing region () is dark brown and 12.5–17.5 μm thick, and the spore-bearing layer (
hymenium) beneath is pale brown and 40–75 μm tall. The
paraphyses (sterile filaments between the asci) are unbranched, about 1.3–2.5 μm wide, with swollen tips; they are glued together but separate when treated with potassium hydroxide (K). The tissue beneath the spore-bearing layer () is pale brown (about 10–15 μm thick), and the layer below that (subhypothecium) is brown (about 10–15 μm thick). The
asci are club-shaped () and comparatively small for the genus, 40–50(–62.5) × 5–10(–15) μm, and typically contain 90–100 spores each. The
ascospores are colourless (
hyaline), usually broadly
ellipsoid (sometimes appearing spherical), 3–5 × 2–3 μm, and stain blue with iodine (I+ blue) and blue-red with iodine–potassium iodide (IKI+ blue-red). ==Habitat and distribution==