Opegrapha dolomitica (images of British lichens)

Thallus thin, white or grey to brown-red, scratching yellow, often more or less immersed in the substrate surface; fruitbodies black, initially small, elliptical to irregular, circular-folded to longitudinally furrowed, opening as slit-like, lirellate apothecia. Best confirmed by microscopic examination of the spores. Widespread but local on damp, base-rich rocks.

Refs: Smith et al. (2009), 638; Purvis et al. (1992), 412 (as O. saxicola); Dobson (2005), 294; Dobson (2011), 297; Wirth (1995), 2: 622, 627 (photo); Puntillo (1996), plate 26 (photo).

lastdragon.org

Images of British Lichens