Caloplaca flavescens (Huds.) J. R. Laundon
Variospora flavescens (Huds.) Arup, Frödén & Sochting
Placodium flavescens (Huds.) A. L. Sm.
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.*