Verrucaria cernaensis Zsch. Cf.

       Thallus rustose 0.1-0.3 mm thick, non-gelatinous, strongly cracked and forming areoles with irregular contours, gray-brown, brown, dark brown. Perithecia submerged in the thallus 2/3 or completely, projecting little and appearing in the form of large blackish or brown-black dots 120-360 µm in diameter. Simple elliptical ascospores, hyaline, without perispore, 18-22 x 9.5-11.5 µm. Pycnidia sometimes present, visible in the form of small brown dots of 40-60 µm. Negative color chemical reactions. Species found on humid siliceous or limestone rocks or near rivers.

N.B. Little-known species taken here: ss. auct. brit. and which could not be analyzed is presented with the usual reservations and Cf.

N.B. According to the British authors this taxon would be the host of Verrucaria polysticta (which is the case here).

Cf. Verrucaria macrostoma whose perithecia are larger and occupy almost all of the areoles.