Thallus pale grey, composed of thick convex areoles (0.30.5 mm) usually in small (to 1 cm diam) patches, but effuse and with thinner thallus with a black fimbriate prothallus when growing on quartzite. Cortex not clearly defined but with a thin (3 m) pale brown layer immediately above the photobiont layer and a hyaline epinecral layer (1050 m) that is I+ violet. Medulla inspersed with numerous fine granules (not dissolving in K or N), I+ violet. Photobiont chlorococcoid, cells 812(15) m.
Apothecia black, lecideine, rounded to angular, occasionally lirellate with slit-like disc, flat 0.40.6 mm diam., proper exciple thick (0.5 mm), raised and persistent. Thecium hyaline, I+ blue, 80100m tall; epihymenium 1015 m thick, brownish-grey (K+ purple-brown; Sedifolia-grey); paraphysoids 1.5 2.0 m thick, septate and moniliform, richly branched and anastomosing, apices swollen to 5 m with dark cap. Asci c. 50 1520 m, broadly sylindrical to sub-clavate, Rimularia-type; ascospores hyaline, simple, 8/ascus, (1315 910 m, thick-walled (c. 1 m thick). Hypothecium hyaline above (subhymenium) of randomly arranged swollen hyphae, pale- to mid-brown merging into the exciple. Excipulum dark brown, cupular, 5070 m wide, of dark-walled, elongated cells 1015 35 m.
Conidiomata not seen.

Chemistry: C, K, KC, Pd. No substances by TLC.

Microscopically similar to Rimularia psephota but with a white, discrete thallus lacking norstictic acid.

Known only from the Falkland Islands and Isla de los Estados.

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