Verrucaria squamulosa Brand & van den Boom

      Thallus discontinuous 2-4 cm in its greatest length, formed of scales and squamules of 0.1-0.5 mm, with rounded edges, tight in the center and overlapping but more and more distant from each other in going towards the edge of the thallus where they can be scattered and isolated against a blackish background, smooth surface, in all shades of green in humid weather, more greenish-brown to greenish-gray in dry weather. Perithecia usually numerous, half immersed in the thallus, subglobular with the base covered by the thallus, black, well-developed involucrellum. Spores broadly elliptical to ovoid, simple, colorless (darker at maturity and taking on a granular appearance), 24-27 x 9-13 µm according to the literature, 20-30 x 15-20 µm according to our measurements. Rare pycnidia. Species occurring on artificial substrates such as concrete, cement, bricks and low acid stones of old walls with high humidity and in the shade, more rarely on damp limestone rocks. N.B. A species very similar to Verrucaria macrostoma with an areolate thallus not formed of isolated squamules (even at the edge) and browner colorings.