Distribution: N - Frl (TSB 21344), Piem (TSB 33202).
Description: Thallus crustose-placodioid, epilithic, forming orbicular rosettes to 8 mm diam., ochraceous yellow to orange, epruinose. Central part of thallus with convex, 0.3-0.6 mm wide areolae which are rarely visible, being covered by crowded apothecia. Marginal lobes highly reduced, 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 inner 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, immersed at first, but basally constricted when mature. Disk concave to convex, orange to reddish-orange, epruinose, smooth. Margin in some cases 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 tall; ; paraphyses septate, scantly branched, sometimes forked, (1.5-)2-3(-4.5) μm wide at the base, with one or two swollen apical cells (2.5-)3- 7.7(-8.5) μm wide; hypothecium colourless. Asci 8-spored, clavate, 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 septum (1.5-)3.4-4.5(-5) μm thick. 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 two critical samples, which however could also belong to other species, so that the occurrence of this species in Italy is dubious.