Description: Thallus crustose, endosubstratic or thinly episubstratic, often minutely granular (granules 15-70 µm in diam.), pale to dark grey-brown, greenish white, or grey-green, sometimes poorly evident. Apothecia biatorine, broadly adnate or slightly constricted at base, 0.2-0.5 mm across, with a concave to slightly convex, reddish brown (when dry) to black (when wet), epruinose disc, and a raised, concolorous or darker, rather thick, finally sometimes excluded proper margin. Proper exciple dark brown to violet-red in outer part, colourless to pale brown within, of radiating, conglutinated hyphae with ellipsoid to oblong lumina; epithecium pale yellow to brown, K-, N-; hymenium colourless, 60-80 µm high, I+ blue; paraphyses simple or sparingly branched in lower part, rather lax, 0.8-1 µm thick at mid-level, the apical cells 2-4 µm wide, often with a dark brown cap; hypothecium colourless or pale brown, K-. Asci (8-)12-16-spored, thick-walled, with a uniformly K/I+ blue apical dome, sometimes with a poorly developed ocular chamber, approaching the Catillaria-type. Ascospores 1-septate, hyaline, ellipsoid or oblong-ellipsoid, often slightly constricted at septum, 9-13 x 5-6 µm, with up to 1.5 µm thick, layered walls. Photobiont chlorococcoid (Dictyochloropsis), the cells 5-9 µm in diam. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a temperate lichen found on trunks of old, mostly broad-leaved trees, often on faces which are seldom wetted by rain, such as undersides of thick branches. On the whole, this is a poorly known species, related to C. atropurpurea, which requires further study. It is included in the Italian red list of epiphytic lichens as “Data Deficient” (Nascimbene & al. 2013c).
Growth form: Crustose
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)