Caloplaca flavescens (Huds.) J. R. Laundon

   Thallus rosette shaped, 3-8 cm; lobes  closely appressed, narrow, contiguous to pleated, smooth to faintly rugose, convex,  lobe-ends not widened,  surface matt, orange  to yellow-orange with frequently a white-whitish ring shaped zone, sometimes the center vanishes or displays a new growth zone. Apothecia often numerous, clustured in the thallus center, to 1-1.5 mm diam., disc plane to slightly convex, orange (often brown-orange to the center), margin faintly paler. Ascospores polarilocular, lemon-shaped, 1-septate, 12-15 x 8-10 µm. Photobiont : trebouxioide. All parts K+ purple. Not specifically maritime, common on the seashore on old walls and nutrient-rich calcareous stones and rocks where it is mixed with other matitime species inducing a possible confusion with notably Caloplaca thallincola. On calcareous rocks, see also taxa of Caloplaca saxicola group, which lobes are short and powdery, and Caloplaca aurantia with flattened lobes towards the margin.