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(Map updated: 11 August 2009)

This is a common crustose lichen of calcareous substrata; it is easily missed or overlooked as Lecidella stigmatea or Sarcogyne regularis (both described elsewhere). The small patches of dark grey thallus are regularly fruiting, the discs black (brown when wetted), without an icing of pruina over the surface and lacking any obvious margin. Sarcogyne regularis can usually be found to have some discs with pruina while Lecidella stigmatea has a green to grey to reddish cast to the thallus and discs fruit gum-like with glossy margins. It is generally frequent throughout Ireland.

Key characteristics

• The small grey thallus (a few centimetres in size at most) with a range of black, convex discs (from pinprick-sized to 1mm diam.) lacking shiny margins and pruina, will usually suffice to identify it
• On limestone headstones, ruined churches, mortared walls and natural outcrops.

Original text submitted by Simon Davey