Verrucaria praetermissa (Trev.) Anzi
Thallus crustose, rather thick, tightly appressed to the substratum, non-gelatinous, areolate or cracked notably when old, grey-whitish, whitish when dry, more white-greenish or grey-greenish when moist, developed on a black basal layer, prothallus absent or pale brownish. Perithecia numerous and more or less regularly ordered, 0.2-0.4 mm, involucrellum not extending laterally, immersed in thallus and limiting the visible part of apex to minute pale brownish or brown-pink dots when young, and to small plane black discs or black rings when old. Ascospores simple, colourless, fusiform with a large corpuscle at the center, 18-25 x 7-11 µm. Photobiont: chlorococcoïde. Chemical spot tests negative. On large granite siliceous rocks subject to periodic submersion on the shores of rivers and streams and occasionally on seepage and damp rocks in shaded and humid woodlands. In areas subject to periodic submersion, most often found with Staurothele fissa and just below the Bacidia inundata and Dermatocarpon luridum zone. N.B. Not to be confused with Herteliana gagei that is blue and seldom fertile. Cf. Verrucaria hydrela with a less cracked and less whitish thallus which comes on more alkaline rocks and more often submerged and whose spores are a little larger.