Tylothallia P.James & H.Kilias
Type : Tylothallia biformigera (Leight.) P.James & H.Kilias [Lecidea biformigera Leight.]
Description : Thallus crustose, thick, areolate to irregularly verrucose, chalky white to creamish to dull green-white; delimited by a wavy, thick, black marginal prothallus. Photobiont green, chlorococcoid, cells 6–12 μm diam. Ascomata apothecia to 1.5 mm diam., plane becoming convex and occasionally tuberculate, irregularly thickened with a verrucose surface, dark grey to blue-black; the disc thinly pruinose, especially at first. Proper exciple apparent when young, becoming excluded at maturity, of richly branched, coherent hyphae, 1–1.5 μm wide, each surrounded by a gel coat swelling in K; K+ yellowish to orange, PD+ pale-yellow. Hamathecium of paraphyses, 1.5–2 μm wide, numerous, slender, often branched and anastomosed, apices slightly swollen, not distinctly capitate, I+ blue. Asci Lecanora -type (Malcolm & Galloway 1997: 186). Ascospores simple to 1-septate, oblong, colourless, without a perispore. Conidiomata pycnidia, immersed. Conidiogenous cells cylindrical, enteroblastic, acrogenous. Conidia ellipsoidal or shortly oblong, simple, colourless.
Tylothallia is included in the family Lecanoraceae (Eriksson et al. 2004; Pennycook & Galloway 2004). Two species are referred to the genus, with one, T. biformigera, known from the Northern Hemisphere (Kilias 1981), and the other, T. pahiensis, known from coastal rocks in SE Australia and New Zealand (Hertel 1983, 1984c, 1987b, 1989b; Rambold 1989; Nordin et al. 1999). Species of Tylothallia differ from Bacidia and Bacidina in having abundantly branched and anastomosed paraphyses, Lecanora -type asci, consistently 1-septate spores, a different chemistry and smaller conidia (Kilias 1981: 393; Ekman 1996a: 45).
