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(Map updated: 11 August 2009)

This lichen is roughly intermediate in size between D. leptophylloides and D. luridum and like them grows on inundated siliceous rocks by rivers and loughs. Along rivers it appears to occupy a zone midway between the submerged and the amphibious so should be regarded as a strict aquatic species. Typically, the pale to dark brown, non-frosted thalli vary between 2-3cm diameter, attached by a single holdfast. The lower surface is darker (almost black) than in related species. It can tolerate silting. Widely distributed in Ireland.

Key characteristics

• Thallus, pale to dark brown above, blackened below
• Intermediate in size; a true aquatic lichen.

Original text submitted by Vince J. Giavarini