Flora, 67: 588, 1884. Basionym: Buellia verruculosa var. jugorum Arnold - Verh. zool.-bot. Ges. Wien, 28: 295, 1879.
Distribution: N - TAA (Scheidegger 1993). C - Sar (Scheidegger 1993).
Description: Thallus crustose, episubstratic, of scattered to adjacent areoles, yellowish white to pale yellow, with a smooth surface, the marginal areoles often slightly elongated and to 1.8 mm long, giving the thallus an almost placodioid appearance; medulla white, I-. Apothecia cryptolecanorine to zeorine, black, 0.3-0.6 mm across, innate to broadly sessile, with a flat to usually convex disc and a thin, finally often excluded proper margin. Proper exciple aethalea-type; epithecium greenish brown, N+ red; hymenium without oil droplets, 50-70 µm high, colourless in upper part, green and N+ red in lower part; hypothecium dark brown. Asci 8-spored, Bacidia-type. Ascospores 1-septate, slightly constricted at septum, oblong-ellipsoid, 11-15 x 6-8.5 µm, thin-walled throughout, Buellia-type, with a microrugulate ornamentation. Pycnidia black, immersed in the thallus. Conidia bacilliform, 6-9 µm long. Photobiont chlorococcoid. Spot tests: thallus K-, C+ persistently orange, KC+ yellow-orange, P-, UV+ orange. Chemistry: arthothelin.
Note: an arctic-alpine to boreal-montane, circumpolar species found on small siliceous pebbles in wind-exposed ridges, sometimes overgrowing other crustose lichens, mostly near and above treeline; probably more widespread in the Alps, certainly rarer in the high Mediterranean mountains.