Description (adapted from Jørgensen & James 1990)
Thallus foliose, oricular, closely adpressed to the rocks or occasionally overgrowing bryophytes, 3-8(-10) cm diam., colonies frequently becoming confluent. Lobes 0.3-0.6 cm wide, leaden grey to pale silvery grey, often somewhat browned, rather fragile, contiguous or frequently overlapping centrally, but often radiating outwards, especially at the margin and ther broadly cuneate to flabellate. Margins ±deflexed, in older part of thallus with lobules. Upper surface plane, initially smooth, in older parts with distinct radiating striae. Lower surface brownish, smooth, mostly without rhizohyphae. Prothallus not developed. Anatomy: heteromerous (90-)100-130 µm wide. Upper cortex paraplectenchymatous 20-30 µm thick of anticlinal hyphae, individual cells ±angular 7-14 x 5-9 µm, not clearly differentialted from the photobiont layer, 30-40 µm wide, which is also paraplectenchymatous with somewhat smaller individual cells and Scytonema filaments, often perpendicularly incorporated, individual cells 6-12 µm diam. Medulla colourless, 40-60 µm wide of densely conglutinate, parellelly aligned periclinal hypahe, below with corticoid, ± cellular structure and there dark brown.
Apothecia infrequent, laminal, sessile, often occuring singly, to 2 mm diam., disc ±concave at first, becoming plane, reddish brown, with thick, raised entire, paler brown proper margin; thalline margin absent. Anatomy: with a paraplectenchymatous proper margin to 100 µm wide, cells arranged in a ± radiating pattern. Subhymenial layers pale brownish to 130 µm wide, of intricately interwoven hyphae. Hymenium to 110 µm deep, colourless, except in uppermost part, where it is pale brownish, I+ deep blue. Paraphyses simple, occasionally branched, 2-3 µm wide, with slightly enlarged apical cells. Asci cylindrical to subcylindrical, 60-90 x 12-15 µm, apically thickened with a blue plug, 8-spored. Spores simple, colourless, broadly ellipsoid 10-15 x 6-10 µm.
Pycnidia ±frequent, immersed, wart-like, blackish, 0.1-0.2 mm diam. Conidia bacillariform 2-3 x 1 µm.
Distribution and Ecology: Known only from the southern South America and Auckland Island (NZ) where it grows on damp acidic rocks.
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