Description: Thallus subleprose, episubstratic, whitish to greyish-green, granulose, poorly delimited, covered with very thin, acicular crystals in herbarium specimens. Apothecia rather rare, arthonioid, more or less round, 0.2-0.7 mm across, at first immersed in the thallus, with a dark brown to black, but densely bluish-grey pruinose, flat to slightly convex disc, without a proper margin. Proper exciple poorly developed, very thin, reddish brown; epithecium reddish brown c. 10 μm high; hymenium colourless to yellowish brown, 60-75 μm high; paraphysoids rather thin, sparingly branched, not or only slightly thickened at apex; hypothecium dark red-brown, conical, up to 60 μm high. Asci 8-spored, broadly clavate to subglobose, approaching the Arthonia-type. Ascospores 3-septate, clearly constricted at septa, more or less bacilliform, 15-20 x 4-6 μm. Photobiont chlorococcoid. Spot tests: thallus K- or K+ pale yellow, C-, KC- or KC+ pale yellow, P-. Chemistry: usnic acid in thallus, perhaps also zeorin.
Note: a mild-temperate species also known from North America, found on the smooth bark of deciduous trees, especially Carpinus; often sterile and overlooked, being easily confused with species of Lepraria.