Thallus of bullate areolae, scattered or contiguous, and to 2.5 mm thick, sooty white or cream-white to brown or greenish white (changing in the herbarium to yellow-brown), shining, areolae to 2 mm broad, occasionally almost pulvinate, sometimes over a white fimbriate hypothallus. Apothecia to 2 mm broad, adnate with narrowed base, black with light gray to blue-gray pruina, when young with thick margin and flat, becoming convex and immarginate; exciple olive-brown or green-brown to greenish black, in older apothecia much reduced and hyaline with incorporated gray (but P+ yellow) granules; hypothecium hyaline; epihymenium blue-green to sooty green-brown; hymenium 40-65 μm, 1+ blue; paraphyses simple or branched and anastomosing, tips thickened to 5 μm; asci clavate; spores short or narrowly ellipsoid, 5-15 x 3.5-8 μm.

Reactions: thallus K+ yellow, P+ orange-yellow, C—, I—; exciple and epihymenium HN03+ slowly red-brown to purple.

Contents: atranorin, psoromic acid, xanthones.

This species grows under overhanging cliffs or on protected sides of boulders, on acid rocks. It was previously known from Greenland, Spitzber-gen, Europe, Asia (Nepal, Konyam Bay on Chukotsk Peninsula), and in North America from Colorado (Anderson 1974). Additional reports are mapped.