Description: Thallus crustose, very thin, often immersed and inapparent, white-grey or grey-brown, without a distinct prothallus. Apothecia lecideine, round, broadly adnate, 0.15-0.3(-0.4) mm across, with a dark brown to dull black, flat to finally convex, epruinose disc and a thin, smooth, raised, finally sometimes excluded proper margin. Proper exciple with a thin, pale to dark brown outer zone composed of pigmented caps of hyphal end-cells, colourless within; epithecium brown-black, K-, N-; hymenium colourless, 30-40 µm high; paraphyses mostly simple, easily made free, 1.5-2 µm thick at mid-level, the apical cells distinctly capitate, up to 6 µm wide, with a cap of dark brown pigment deposited within the hyphal wall; hypothecium pale to dark brown at least in upper part, paler in lower part. Asci 8-spored, clavate, with a K/I+ blue outer coat and a K/I+ uniformly blue apical dome, Catillaria-type. Ascospores 1-septate, hyaline, oblong-ellipsoid, (7-)8-10(-12) x (2-)2.5-3.5(-4) µm, thin-walled, without a perispore. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a mainly mild-temperate, holarctic species found on isolated deciduous trees, also in rather disturbed habitats, e.g. in parklands, and on wayside trees, sometimes growing as a parasite on other lichens (Brackel 2015). For the distinction towards C. mediterranea and C. servitii see Tretiach & Hafellner (1998).