Distribution: N - Frl (TSB 21344), Piem (TSB 33202).
Description: Thallus crustose-placodioid, episubstratic, forming orbicular, up to 8 mm wide rosettes, ochraceous yellow to orange, epruinose. Central part of thallus with convex, 0.3-0.6 mm wide areoles which are rarely visible, the thallus center being covered by crowded apothecia; marginal lobes highly reduced, sometimes hardly visible, strongly convex, 0.3-0.8(-1) mm long and (0.1-)0.2-0.8(-1) mm wide. Upper cortex well developed, (15-)20-80 μm thick, with a 5-30 μm thick orange upper layer, and a hyaline lower layer with irregularly arranged hyphae. Apothecia lecanorine to zeorine, sometimes pseudolecanorine, abundant, 0.2-2.5(-4) mm diam., usually deformed by mutual compression, forming clusters on the lobe bases and areoles, at first immersed, then sessile and basally constricted, with a concave to convex, orange to reddish-orange, epruinose, smooth disc and a margin which in some cases is clearly differentiated in an orange, 30- 50 μm thick proper margin and a 40-150(-200) μm thick, usually persistent and often prominent thalline margin. Epithecium (6.5-)10-14 μm thick, brownish-yellow, K+ red; hymenium colourless, 50-30(-92) μm high; araphyses septate, sparingly branched in upper part, (1.5-)2-3(-4.5) μm wide at base, the apical cells (2.5-)3- 7.7(-8.5) μm wide; hypothecium colourless. Asci 8-spored, clavate, functionally unitunicate, apically thickened with a broad internal beak, the inner part of apex and external cap I+ blue, Teloschistes-type. Ascospores 1-septate, polarilocular, hyaline, narrowly ellipsoid, (9-)11-14.5(-18.5) x (4-)5.8-6.5(-7.5) μm, the equatorial thickening ("septum") (1.5-)3.4-4.5(-5) μm. Photobiont chlorococcoid. Spot tests: thallus and apothecia K+ red, C-, KC-, P-. Chemistry: thallus and apothecia with parietin (major), fallacinal, emodin, teloschistin and parietinic acid (minor), corresponding with chemosyndrome A of Søchting (1997).
Note: a very poorly understood species (see Gaya 2009), purportedly growing on both calcareous and siliceous rocks. The greatest majority of Italian samples filed under this name proved to belong to C. pusilla, except a few critical samples, which however could also belong to other species, so that the occurrence of this species in Italy is dubious.