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© Mike Simms

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(Map updated: 11 August 2009)

This species grows on rocky seashores lapped by unpolluted waters. The first thing to notice is the blue-grey, knotted-granular thallus mixed up with isidia consolidated into a whole, like pebble-dashed concrete left to set. Discs (to 1mm diam.) are common, orange-brown with a conspicuous, notched margin. Spot reactions are negative but its presence in the vicinity of nutrient-enriched rock is worth noting. Throughout Ireland but rarer in the south-east.

Key characteristics

• Blue-grey thallus of knotted granules, set like concrete
• Discs orange-brown with margins notched; rocky, nutrient-enriched seashores.

Original text submitted by Vince J. Giavarini