Description: Thallus crustose, mostly endosubstratic and poorly evident, consisting of more or less scattered goniocysts provided with a cortex of isodiametric, brown-capped cells. Apothecia black, epruinose, sessile, constricted at base, 0.3-0.8 x 0.2-0.4 mm, from narrowly elongate to angular or more or less rounded, with a initially slit-lixe, later expanded and sometimes gyrose-umbonate disc, and a prominent, more or less inrolled proper margin. Proper exciple cupulate, dark brown to brown-black, up to 65 μm wide; epithecium brown; hymenium colourless to pale yellow, 30-55 μm high, I+ weakly blue; paraphyses coherent, 1-1.5 μm thick at mid level, simple or sparingly branched and anastomosing in upper part, the apical cells only slightly thickened (< 3 μm); hypothecium dark brown, in continuation with the exciple. Asci 8-spored, clavate to subcylindrical, I+ blue after pre-treatment with K, with a light amyloid tissue throughout, but with darker staining regions around the apex and in a narrow zone below the inner upper wall of tholus. Ascospores 1-celled, hyaline, broadly ellipsoid, 4-6(-8) x 2-4.5 μm, not halonate. Photobiont chlorococcoid. Spot tests: K-, C-, KC-, P-, UV-. Chemistry: thallus without lichen substances.
Note: on lignum, especially on vertical sides of stumps, with optimum in the subalpine belt; certainly more widespread in the Alps.