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, delimited by a black prothallus which is often also visible between the areoles as a hypothallus, often mosaic-forming. Medulla white, more or less amyloid. Apothecia lecideine, (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, inner hyphae narrow, hyaline, prosoplectenchymatous, outer hyphae parallel, moderately swollen and usually strongly carbonized with brown and aeruginose pigments reacting N+ violet; epithecium brown to olive, N+ violet; hymenium colourless, not inspersed; paraphyses simple to moderately branched, apically swollen, with a brown pigment cap. Asci 8-spored, clavate, Bacidia-type. Ascospores 1-septate, brown, broadly ellipsoid with obtuse ends, thin-walled throughout 13-18(-20) x 8-10.5(-12) x 7-10(-12) µm, the wall microrugulate. Pycnidia rare, urceolate to globose, unilocular. Conidia bacilliform, 5-7 x c. 1 µm. Photobiont chlorococcoid. Spot tests: thallus and medulla 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.