Thallus crustose, effuse, superficial, grey to ochraceous-brown, matt, sometimes weakly rimose, not corticate, to 200 µm thick but sometimes evanescent. Photobiont chlorococcoid, with cells 7-12 μm diam.
Anamorph: conidiomata pycnidia, 30-50 µm diam. [50-90 µm diam. fide Lutzoni & Brodo 1995], immersed, the wall dark blue-green. Conidiogenous cells flask-shaped. Conidia 3-5 × 0.8-1 μm.
Teleomorph: ascomata aspicilioid apothecia, 150-300 µm diam., immersed in the thallus, the disc slightly concave, black (tinged blue-green when wet). Proper margin inconspicuous, blue-green above. Hymenium 60-80 μm tall, immersed in gel, colourless below, pale to dark blue-green above, K–, N+ crimson, without a distinct epithecium. Hypothecium hyaline. Interascal tissue of septate paraphyses (1-)1.5-1.7 μm diam., sparingly branched below, more frequently near the apices, which are slightly swollen (to 3 μm diam.) and sometimes weakly moniliform. Asci 60-70 x 20-23 µm, broadly clavate, short-stalked, the apex rounded, with a uniformly K/I+ blue apical dome and K/I+ blue, fuzzy, outer coat forming a thick cap over the apex, 8-spored. Ascospores arranged biseriately, 11-13.5 x 8-10 µm [12-18 × 7-9 μm fide Coppins et al. 2009, 14-17 x 7.5-10 µm fide Lutzoni & Brodo 1995], broadly ellipsoidal, aseptate, hyaline, fairly thick-walled, smooth, without an epispore or gelatinous sheath.
Chemistry: no lichen substances detected by TLC.
Assessed by Woods & Coppins as of Least Concern, but listed as Nationally Rare.
Scattered tthroughout Northern England and Scotland, with a single record from mid Wales. BLS map here.
On calcareous rocks near rivers, calcareous pebbles in coastal dunes and shingle ridges.