Description: Thallus crustose, areolate, brown-grey to grey, 100-500 μm thick, forming irregular, up to to 3 cm wide patches, often starting the life-cycle on the thalli of other crustose lichens. Areoles angular to rounded, flat to slightly convex, usually contiguous, 0.1-0.5 mm thick. Epinecral layer often present, to c. 10 μm thick; cortex of spherical, thin-walled cells, K+ violet, N+ red in section; medulla well-developed only in thick thalli, of loose prosoplectenchyma, non amyloid. Apothecia frequent, zeorine, (0.3-)0.5-0.9(–1.3) mm across, with an initially orange, then dark orange brown to brown disc surrounded by a yellow to orange proper margin and by a grey thalline margin. Epithecium orange-brown, granular, K+ red C+ purple in section; hymenium colourless, c. 70–110 μm tall, amyloid; paraphyses 2.0–2.5 μm thick in lower part, but gradually widening to 4-5 μm in upper part; hypothecium colourless, rarely with a few oil droplets, amyloid, with a subhypothecial algal layer. Asci 8-spored, clavate, Teloschistes-type. Ascospores 1-septate, polarilocular, hyaline, ellipsoid (8-)12–15(-17) x (5-)7-8(-9.5) μm, the septum (4-)5-6(-7) μm thick. Pycnidia appearing as dark grey dots. Conidia ellipsoid to tear-shaped. Spot tests: thallus K-, C-, KC-, P- (but sections of cortex K+ violet, N+ red); apothecial disc and proper margin K+ red, C+ purple in section. Chemistry: cortex and top of pycnidia with the Sedifolia-grey pigment; apothecia with chlorinated anthraquinones.
Note: a mild-temperate, characteristic, but much misunderstood species found on the top of calcareous birds' perching boulders; in northern Italy is mostly found at low altitudes, in southern Italy it reaches the montane belt. This species was often synonymised with C. spalatensis Zahlbr., but according to Vondrák & al. (2013), the holotype of the latter species, contrary to what stated in the description, grows on siliceous rocks and has biatorine apothecia, being a poorly developed Blastenia.