Porina lectissima  (Fr.) Zahlbr.

    Thallus crustose, superficial, tightly attached to the substratum, thin, more or less cracked, muddy brown, pale brown, olive-brown, brown-yellowish, brown-orange, slightly greenish when moist. Perithecia mostly immersed in the thallus, hemispherical to conical-hemispherical, 0.3-0.5 mm diam., reddish to brown-reddish, apices brown-blackish when dry, red when moist, turning to dark brown-black when old. Pycnidia immersed in the thallus, numerous, orange when moist. Ascii 8-spored, cylindrical, apices pointed. Ascospores colourless, lengthy ellipsoid to fusiform, 3-septate, 16-30 (40) x 4-6 µm according to literature, 20-25 x 5-7 µm according to our measures. Photobiont: Trentepohlia. Chemical spot tests negative. Rare in our prospection area, on damp siliceous rocks on river banks or along shaded streams and rivers. This species might be understated and go unnoticed due to its aspect (muddy smudge aspect) and requires a careful observation of its peculiar habitat. N.B. Porina leptalea is rather similar with smaller perithecia and ascopores; in addition, seldom found on damp rocks.