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(Map updated: 11 August 2009)

This aquatic, crustose lichen with radiating lobe margins is a submerged-zone species of rivers and streams so it is best to hunt for it during periods of low water or in times of drought. It may occur as scattered fragments or as dominant colonies, but is always an attractive, eye-catching species. The thallus takes the form of dark-orange-brown circular or semicircular patches up to 6cm diameter; these often joining up to form large colonies a metre or so wide on rivers with extensive exposures of flat bedrock. Discs are frequent resembling low, knobbly warts. Western Ireland; probably under-recorded.

Key characteristics

• A submerged lichen, forming neat, orange-brown, circular colonies; discs take the form of knobbly warts
• Placynthium flabellosum is similar but looks like a submerged Phaeophyscia; it has smooth marginal lobes, and is never orange-brown as in P. kenmorensis.

Original text submitted by Vince J. Giavarini