Petractis luetkemuelleri (Zahlbr.) Vezda

   Thin thallus, on the surface of its substrate and partially encrusting, minutely rugose, presence of minute sinuous whitish veins (calcite?), grey-pink, pink, dull whitish-pink, pale salmon (only when fresh, otherwise white-greyish, pale ochre-greyish, pale greyish), margin undeterminate, prothallus absent or undeterminate. Apothecia sometimes numerous, totally or to 3/4th immersed in the thallus, 0.4-0.5 mm diam., disc concave to flat, beige-pink when fresh, or ochraceous, pale brown-yellowish, pale brown, exciple thick, petal-shaped at first, more or less wraping the disc, whitish. Ascii 8-spored, 100-120 x 10-14 µm. Ascospores highly variable, ellipsoid, colourless, wraped by a gelatinous perispore halo-forming, 3-transversely septate, (rarely with muriform tendencies or 3-4 septate), 18-30 x 7-10 µm. Photobiont: Trentepohlia sometimes forming orange spots visible in eroded sections of the thalli or even free in old specimen. Thermopilic and Mediterranean species, very rare in our propection area, restricted to well-lit vertical walls of hard limestone rocks near the seashore. N.B. In the same sites but on more soft and humid limestones a slightly different but inconspicuous morph may be found,  Ramonia calcicola, with smaller apothecia, a more rugose or granular thallus with more or less pink tinges. See also Petractis clausa of which apothecia are much larger, ascospores strictly 3-septate and photobiont different (Scytonema).