Ab omnibus speciebus generis Cliostoma habito saxicola et thallo atranoro unico continenti differt.
Typus: Falkland Islands, East Falklands, Port William, between Yorke Bay and Whalebone Cove, UTM21F VC 4473 [51°684000’S, 57°796000’W], 75 ft. [23m], outcrops on clay ridge, 1 February 1968, H. A. Imshaug (41673) & R. C. Harris (MSC-0111545—holotypus).
Description
Thallus effuse, consisting of small, discrete patches up to 0.5 mm across, but forming larger patches in depressions; areolate, areoles c. 0.1 mm across; creamy white with a minutely arachnoid surface, cortex absent; often with a black, fimbriate prothallus. Medulla with numerous minute crystals giving it a pale brown colour, mostly dissolving in K. Photobiont chlorococcoid, cells 10–12 mm diam.
Apothecia lecideine, black, blue-black when wet, ±orbicular to slightly elongate, often with a wavy margin, 0.3–0,6 mm diam., flat to convex, ±immarginate; flat with a thin proper margin when young, margin 0.02 mm wide, concolorous with disc or unpigmented; disc rough. In section:proper exciple poorly developed with narrow anastomosing medullary hyphae with swollen, ±blue-black pigmented cortical cells; with numerous minute colourless crystals dissolving in K. Hymenium 35–40 mm tall; paraphyses unbranched, sparingly branched towards apex, septate, lax in K, c. 2 mm wide, slightly swollen to 3 mm at apex, upper 5–10 mm with blue-black pigment; epihymenium granular with scattered minute colourless crystals, mostly dissolving in K. Hypothecium hyaline, composed of randomly orientated hyphae. Asci ±cylindrical when young, becoming becoming clavate, Bacidia-type, 25–30 × 12– 20 mm; ascospores hyaline, 1-septate, 9–11 × 4–5 mm.
Conidiomata not observed.
Chemistry. C--, K+ yellow, Pd--; atranorin by TLC.
Distribution and ecology. Known only from the type collection, which is on the upper surface of a flat, angular quartzite pebble, c. 10 × 5 cm in area.