Thallus strongly encrusted in the bark, more or less smooth, cream, pale gray, greyish-brown, olive-gray, rarely bordered by a dark brownish hypothallus. Apothecia of 1-2 mm, included or on the surface of the thallus, misshapen, irregularly rounded, very often as if broken into several fragments, blackish-brown. Spores oblong, colorless but light brown at the end, muriform "rubber boot imprint" with 4-9 transverse septa and 1-3 longitudinal septa, 17-24 x 7-10 µm according to literature, 18-25 x 8 -10 µm according to our measurements. Pycnidia blackish-brown. Photobiont: Trentepohlia. C-, K-, KC-, P-. Uncommon species occurring on the smooth bark of deciduous trees in forests with a temperate oceanic climate.