12. Pyxine petricola Nyl. , in J. M. Crombie, Journ. Bot. 14: 263 (1876).

Lectotype (designated here):—ISLAND OF RODRIGUEZ, 9 December 1874, I. B. Balfour 2391 (Transit of Venus Expedition) (BM!, isolectotypes H-NYL 31754! and H-NYL 2336, insertum post mortem). — Pyxine subvelata Stirt., Trans. Proc. New Zealand Inst. 30: 396 (1898). Holotype:— AUSTRALIA. Queensland; Jimbour, June 1895, F. M. Bailey s.n. (BM!). For further synonymy see Kalb (1987).

Thallus corticolous or saxicolous, 2–6 cm wide, adnate to loosely adnate. Lobes radiating or irregular, contiguous to imbricate, plane to concave, rarely convex, 0.7–1.2 mm wide, subrotund to truncate at the apices. Upper surface white to pale grey, greenish grey or yellowish grey, pruinose in patches or seldom only punctiform, matt or glossy; polysidiangia, soralia and isidia absent. Pseudocyphellae ± distinct, marginal and laminal, usually restricted to the peripheral parts of the lobes, rarely becoming reticulate. Medulla uniformly white. Lower surface black in the centre, paler towards the margin; rhizines dense, short, simple or ± furcate. Apothecia cocoës - type, 0.5–1.5 mm wide; disc epruinose. Internal stipe distinct; upper part rose to orangered, K+ purple, P-; lower part white, K-, P-. Ascospores 14–20 × 5–9 µm. Conidia bacilliform, 3–4 × 1 µm.

Chemistry: Cortex K-, UV+ yellow; medulla K-, C-, KC-, P-; containing lichexanthone (major), terpenes (major or minor).

Distribution and habitat:—Occurs on rock and bark in dry dipterocarp and mixed deciduous forests. Also in Australia, Asia, Africa, South America and the Pacific (Hawaiian Islands and Micronesia).

Notes:— Pyxine petricola is characterized by the adnate to loosely adnate thallus, the absence of soredia, isidia and polysidiangia, the white medulla, cortical lichexanthone and cocoës - type apothecia with an internal stipe that is reddish in the upper part.

Material from Thailand examined:— Loei; Phu Luang Wildlife Sanctuary, Phu Ho Forest Ranger Station, on the bark of Sandoricum koetjape in mixed deciduous forest, 569 m, 17°07'13'' N, 101°34'30'' E, 29 July 2009, MSPL 375 (RAMK).— Sakonnakon; Ratchapat Sakonnakon, on the trunk of Mangifera indica in dry dipterocarp forest, 300 m, 19 March 1998, W . Khumtim 11889 (RAMK).