Thallus white or greenish-white or pale green-grey, closely attached, spreading in rounded patches, to 8 (rarely to 20) cm diam., corticolous. Upper surface rough, chalky, minutely areolate-cracked, areolae angular or plane, 0.2-0.3 mm diam., separated by narrow cracks. Apothecia lecideine, sessile, constricted at base, 0.5-1 mm diam., crowded in groups or dispersed, disc concave at first, becoming plane or subconvex with age, white-pruinose at first, becoming brownish-grey or bluish-pruinose when mature, often gyrose centrally, proper margin distinct, white-pruinose to blackish, entire or crenulate, or distorted by mutual pressure. Hymenium 140-160 µm tall, blackish above, pale brownish below. Asci clavate, rounded at apices, walls thickened, 85-90 × 13-15 µm. Ascospores 3-4-seriate, acicular, apices rounded, straight or slightly curved, 11-13-septate, 36-45 × 3 µm. Chemistry: Schizopeltic acid and an unidentified (UV+ violet) compound.