Synonyms: Buellia aethaleoides (Nyl.) H. Olivier; Buellia atropallidula (Nyl.) J. Lahm; Buellia baltica Erichsen; Buellia impressula (Leight.) A.L. Sm.; Buellia nigerrima (Nyl.) Arnold; Buellia sororia Th. Fr.; Buellia sororioides Erichsen; Buellia subatra Erichsen; Buellia verruculosa (Sm.) Mudd non auct.; Lecidea atroalbella auct. non (Nyl.) Nyl.; Rinodina immersata (Nyl.) H. Olivier; Rinodina ocellulata Bagl. & Carestia; Rinodina umbrinofusca (Nyl.) H. Olivier
Distribution: N - Frl (Tretiach & Hafellner 2000), TAA, Lomb (B-60 0195402), Piem (Isocrono & al. 2003, 2004, Favero-Longo & al. 2004, 2015), VA (Matteucci & al. 2015c), Lig. C - Tosc, Sar (Scheidegger 1993, Nöske 2000, Rizzi & al. 2011, Neuwirth 2018). S - Camp (Aprile & al. 2002), Bas (Jatta 1909-1911), Si (Grillo & Caniglia 2004).
Description: Thallus crustose, areolate, grey to pale brown, dull, epruinose, phenocorticate, often mosaic-forming, forming up to 2 cm wide patches delimited by a black prothallus which is often also visible between the areoles as a hypothallus, the areoles 0.2-0.6(-1.2) mm wide, contiguous, flat to convex. Medulla white, more or less amyloid. Apothecia cryptolecanorine or zeorine, (0.1-)0.2-0.4(-0.7) mm across, remaining immersed in the thallus, angular to irregularly circular, mainly in the centre of areoles, with a black, epruinose, flat disc and a usually indistinct proper margin, sometimes surrounded by a thalline collar. Proper exciple poorly differentiated, aethalea-type, the inner hyphae narrow, hyaline, prosoplectenchymatous, the outer hyphae parallel, moderately swollen and usually strongly carbonized with brown and aeruginose pigments reacting N+ violet-red; epithecium brown to olive, N+ violet-red; hymenium colourless, not inspersed with oil droplets; paraphyses simple to moderately branched, apically swollen, with a brown pigment cap; hypothecium almost colourless to dark brown. Asci 8-spored, clavate, Bacidia-type. Ascospores 1-septate, brown, broadly oblong with obtuse ends, (9.5-)13-18(-20) x (4.5-)7-10(-12) µm, Buellia- type, thin-walled throughout, the wall microrugulate. Pycnidia rare, urceolate to globose, unilocular. Conidia bacilliform, 5-8 x c. 1 µm. Photobiont chlorococcoid. Spot tests: K+ red (needle-like crystals), C-, KC-, P+ yellow, UV-. Chemistry: norstictic and connorstictic acids.
Note: on horizontal to weakly inclined, exposed surfaces of hard, crystalline siliceous rocks wetted by rain, mostly in species-poor stands, common only in dry areas.