• Arthonia atlantica P.James
Arthonia atlantica
Click on map to open large map in new window
(Map updated: 11 August 2009)

Click here to view an interactive map of the Northern Ireland dataset as currently collated by CEDaR.
The map is generated through the NBN Gateway using their Interactive Mapping Tool.


This species grows below dry siliceous underhangs and in sheltered recesses in walls near the coast. It has a pale grey, scurfy thallus which looks unimpressive at first sight. However, closer inspection shows the presence of numerous iced-over discs joined together in a continuous mosaic reminiscent of Enterographa. Spores are two- to four-septate with an enlarged upper cell. The thallus tests Pd+ pale yellow or red. In Ireland, it is a western oceanic species and is known from Counties Kerry, Cork, Galway and Mayo, especially the offshore islands.

Key characteristics

  • Small, white to pale grey mosaic-forming crust with hidden Enterographa-like frosted discs; spores with enlarged upper cell
  • On the sheltered underhangs and shaded recesses of cliffs and walls along western coasts; Peterjamesia circumscriptum scratches orange with a finger nail.

Original text submitted by Vince J. Giavarini

 Simms, M. J., (2016). Arthonia atlantica P.James. [In] LichenIreland. Accessed on 2018-07-23.