Thallus blue-grey, more rarely grey-brown, of scattered to usually coalescing convex to globose areoles 100-400 µm diam., often proliferating to form a thick crust; areoles matt, fragile, eroding to form sorediate patches, the soredia 20-50 μm diam., the outer hyphae greenish, K–, N± red. Photobiont cells 4-7 μm diam.
Anamorph: not known.
Teleomorph: ascomata apothcia, 200-600 (-1000) µm diam., sometimes tuberculate, flat to convex, shining black. True exciple well-developed, hyaline. Hymenium 40-55 μm tall, usually greenish to blue-green (K-, N± red) in the upper part. Hypothecium ± hyaline. Interascal tissue of numerous net-like pseudoparaphyses 1-1.5 μm diam., branched especially above, the apices often thickened to ca 2.5 μm with a layer of green pigment. Asci 40-55 × 12-17 μm, clavate, without a clear ring structure, 8-spored. Ascospores 14-26 (-29) × 4-5.5 μm, cylindric-ellipsoidal to fusiform, ± curved, (1-) 3-septate, hyaline, fairly thin-walled, smooth, without an epispore or gelatinous sheath.
Chemistry: thallus C+ red, K–, Pd+ red; apothecial sections C+ red; argopsin and gyrophoric acid.
Assesed by Woods & Coppins (2012) as of Least Concern.
Common, mainly in N & W Britain, scattered in Ireland. BLS map here.
On bryophytes and plant debris on acid rocks and peaty ground, less often on bark or wood.