Rhizocarpon thomsonii Zahlbr.
Holotype: New Zealand. Otago, Mac's Valley near Dunedin. On rock. J.S. Thomson ZA 15, W -not seen.
Thallus crustose, orbicular to spreading, to 8 cm diam., areolate, prothallus indistinct or absent. Areolae small, 0.2-0.3 mm diam., greyish-white, plane to convex, often almost nodular-papillate, separated by narrow black, cracks. Apothecia crowded, scattered, sessile, rounded, black, shining, epruinose, 0.5-1 mm diam., plane to convex, margins prominent, entire. Hymenium brownish, 120 µm tall. Paraphyses filiform, not much branched. Hypothecium thick, brown-black. Asci 8-spored, oval-clavate, apices rounded. Ascospores triseriate, colourless to brownish, ellipsoid, apices rounded, muriform, 18-23 × 7.5-9 mm, surface corrugate.
S: Otago. Known only from the type collection.
Endemic
