Caloplaca saxicola (Hoffm.) Nordin

   Thallus rosette-shaped, 1-5 cm diam., margin minutely lobate, center crustose and granular, margin lobes short, narrow, 0,5-1,5 mm wide, convex or swollen, matt and cristal powdered, yellow to orange, dark orange. Apothecia usually abundant and crowded, 0,5-1 mm de diam., disc flat at first but subconvex at maturity, red-orange to brown-orange, margin conspicuous at first, excluded when mature, yellow-orange to orange. Ascospores polarilocular, 8-16 x 3-7 µm, septum 2-4 µm wide. Photobiont: trebouxioide. Thallus and apothecia K + purple. On calcareous well-lit rocks and, mortar and chapel walls exposed to South. This species is considered here sensu lato since Caloplaca saxicola is a community of taxa that led authors to multiple interpretations. Recent molecular markers analyses demonstrated that 2 groups are present: the Caloplaca arnoldii group with 4 taxa and the Caloplaca saxicola group with 7 taxa. The most frequent species belonging to the Caloplaca saxicola would be Caloplaca pusilla wich probably is the least abundantly found at the Head of Brittany. See Caloplaca flavescens very common on concrete or walls, with brighter colours, less swollen and more flattened marginal lobes, and  Caloplaca scopularis growing on weakly acidic rocks or walls near the seashore and with lobes not powdery and apothecia markedly sessile.*