Thallus squamulose, becoming minutely subfruticose, in patches, to 10 cm diam., forming a dense, caespitose mat. Squamules crowded, nodular-papillate, flattened or subterete 0.2-2 mm tall, 0.1-0.4 mm wide, greyish-black above, yellowish-brown below, blackened at apices, often distinctly white-pruinose, occasionally squamules may enlarge to forma lobate, dorsiventral, foliose rosette with laciniate margins to 5 mm diam., anchored to the substrate with short, black rhizines. Apothecia sessile, small, to 0.5 mm diam., often numerous and projecting above squamules, disc plane, dark brownish to black, shining, without pruina, proper margin thin, concolorous with thallus, often excluded in older fruits. Ascospores irregularly biseriate, rarely uniseriate, ellipsoid with rounded apices 11-14 × 5-7 µm.