Distribution: N - VG (25437), Frl, Ven (Watson 2014), Lomb (Lazzarin 2000b), Emil (Fariselli & al. 2020). C - Tosc (Tretiach & al. 2008), Marc (Nimis & Tretiach 1999), Umb (Ravera & al. 2006). S - Camp (Nimis & Tretiach 2004), Pugl (Nimis & Tretiach 1999), Bas (Nimis & Tretiach 1999), Si (Nimis & al. 1994, 1996b).
Description: Thallus crustose, entirely endosubstratic, whitish or poorly evident. Apotecia lecideine, 0.2-0.3(-0.4) mm across, yellowish brown to pale reddish brown, sessile, with a concave, then flat to slightly convex disc, and an initially prominent and smooth, finally excluded proper margin which is usually paler than disc. Proper exciple pale yellow in outer part, colourless within; epithecium pale yellowish brown, K-; hymenium colourless, 45-60 µm high; paraphyses simple, the apical cells only slightly swollen, up to 2.5(-3) µm wide, weakly pigmented; hypothecium colourless to pale straw-coloured. Asci 8-spored, clavate, surrounded by a gelatinous I+ blue coat, with a well-developed I+ blue tholus, a I+ darker blue tube and a well-developed ocular chamber, approaching the Bacidia-type. Ascospores 1-septate, slightly restricted at septum, hyaline, ellipsoid to ovoid-fusiform, (10-)12-16(-18) x 4-6.5 µm, the old ones with a microrugulate surface. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a mild-temperate species found on steeply inclined or underhanging faces of compact limestones in sheltered situations, e.g. in narrow gorges along creeks.