Rimulariae psephotae similis sed thallo albido, uno centimetro diametro, et acidum norsticticum absenti.
Typus: Falkland Islands, West Falkland, Fox Bay, N of East Head, UTM 21F TC 9435 [51°992667’S, 60°000833’W], along shore, 7 February 1968, H. A. Imshaug (42143) & R. C. Harris (MSC-0136487— holotypus; BCRU—isotypus).
Thallus white to pale grey, composed of thick convex areoles (0.3–0.5 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 mm) pale brown layer immediately above the photobiont layer and a hyaline epinecral layer (10–50 mm) that is I+ violet. Medulla with numerous fine granules (not dissolving in K or N), I+ violet. Photobiont chlorococcoid, cells 8–12(–15) mm.
Apothecia black, lecideine, rounded to angular, occasionally lirellate with slit-like disc, flat 0.4–0.6 mm diam., proper margin thick (0.5 mm), raised and persistent. In section:proper exciple dark brown, cupular, 50–70 mm wide, of dark-walled, elongated cells 10–15 × 3–5 µm. Hymenium hyaline, I+ blue, 80–100 mm tall; epihymenium 10–15 mm thick, brownish grey (K+ violet-brown; sedifolia-grey); paraphysoids 1.5–2.0 mm thick, septate and moniliform, richly branched and anastomosing, apices swollen to 5 mm with dark cap. Asci c. 50 × 15–20 µm, broadly cylindrical to sub-clavate, Rimularia-type; ascospores hyaline, simple, 8 per ascus, 13–15 × 9–10 µm, thick-walled (c. 1 mm thick). Hypothecium hyaline above (subhymenium) of randomly arranged swollen hyphae, pale to mid brown merging into the exciple.
Conidiomata not seen.
Chemistry. C--, K--, KC--, Pd--. No substances by TLC.