Arthonia tumidula (Ach.) Ach.
Spiloma tumidula Ach., Meth. Lich.: 11 (1803).
Thallus shining in parts, slightly roughened in others, pale grey-brown, sometimes tinged red or pinkish, in patches delimited by a ± well- defined black or brownish line, or immersed. Ascocarps frequent, scattered irregular to ± lirelliform, sometimes bluntly stellate with a pale brown to blackish disc which is pink-white or red-pruinose at margin, 0.2 mm wide to 1-2 mm long. Ascospores obovate-oblong, 3-5-septate, 15-26 × 5-8 µm, upper cell larger.
N: Known only from one collection. Sine loco. C. Knight (BM).
Cosmopolitan
