Byssoloma marginatum (Arnold) Sérus. Cf.

   Thallus thin and not always distinct, 3-4 cm at its greatest length, continuous and a little mealy, greenish-white, pale greenish. Apothecia numerous, 0.3-0.6 mm in diameter, often grouped or aggregated, flat disc at first then quickly convex and even globose, dark gray-brown, blackish, black sometimes with blue reflections, lighter margin slightly prominent at the beginning then fading at the end. Young and fresh apothecia seem to rest on a small whitish cottony ring but this disappears in old apothecia. Hypothecium dark chocolate. Elliptical ascospores, 3-septate, 12-18 x 3-5 µm according to the literature; 11-16 x 4-5 µm according to our measurements. Conidia abundant, pyriform, 4-4.5 x 1.3-1.7 µm. No significant color chemical reactions. Rare species found in moss on tree bark in very humid areas.

N.B. The taxon presented here was found on the bark of a Populus, as it has crossed characteristics with other taxa of the genus we present it with the usual reservations.