Distribution: N - Frl (TSB 26480), Ven (TSB 19719), TAA (Šoun & al. 2011), Lomb, Piem. C - Abr (TSB 24914).
Description: Thallus crustose, episubstratic, areolate, up to 0.4(-0.8) mm thick, pale to very dark grey or almost black in sun-forms, usually with a bluish tinge, often delimited by a narrow, black prothallus. Areoles first convex, then flat, up to 2 mm wide, isidiate; isidia arising mainly from margins, but soon covering the whole surface, globose to shortly elongated, concolorous with thallus, in average 82 μm wide. Upper cortex paraplectenchymatous; medulla poorly developed. Apothecia lecanorine, up to 1.3 mm across, sessile, with a flat to slightly convex, pale to dark orange disc and a thick, raised, sometimes crenulate or isidiate thalline margin. Proper exciple indistinct, up to 10 μm thick, prosoplectenchymatous; epithecium orange, with inspersed granules, K+ red; hymenium colourless, 55-85 μm high; paraphyses simple to branched, 2 μm thick at base, the uppermost cells slightly swollen, 3–5 μm wide; hypothecium colourless. Asci 8-spored, clavate, Teloschistes-type. Ascospores 1-septate, polarilocular, hyaline, ellipsoid, 10-15 x 5-8 μm, the septum 3-6 μm thick. Pycnidia rare, immersed. Conidia bacilliform, c. 3 × 1 μm. Photobiont chlorococcoid. Spot tests: thallus K- or K+ violet, C- or C+ violet, KC-, P-; disc of apothecia K+ red. Chemistry: thallus with the Sedifolia-grey pigment; disc of apothecia with parietin (major), fallacinal, emodin, teloschistin and parietinic acid (minor).
Note: a calcicolous species of nutrient-enriched rocks in upland areas. See also note on C. chlorina.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by isidia, or isidia-like structures (e.g. schizidia)