Tremolecia atrata (Ach.) Hertel
Gyalecta atrata Ach., K. Vet. Acad. nya Handl.: 299 (1808).
Thallus 3-40 mm diam., forming a crust, 0.2 mm thick, ochraceous to rust- red to dark grey or blackened, cracked and irregularly areolate, surrounded by a marginal black prothallus. Apothecia numerous, 0.1-0.4(-0.7) mm diam., discrete or crowded in compact clusters, semi-immersed or sessile, disc black with a well-developed swollen margin, concave to plane. Excipulum massive, coal-black. Asci clavate, 55 × 15 µm. Ascospores ellipsoid 10-13(-17) × 6-7.5(-10) µm.
S: Temple Peak (Arthur's Pass) 1830 m, Mt Alack, Fox Glacier 2550 m. On alpine rocks, probably more widespread in mountainous areas in New Zealand than present records show.
Cosmopolitan
The coal-black excipulum is characteristic.
