Odonthalia dentata (Linnaeus) Lyngbye
Murlough Bay, Co Antrim, Northern Ireland. 30 August 2005.
Picture © Bernard Picton, Ulster Museum.
Description: Cartilaginous, strongly compressed, two-edged, deep purplish-red fronds, much branched, to 300 mm long, from hard, conical disc. Branching distichous, irregularly pinnate, branches deeply pinnatifid, segments with large, alternate teeth distally. Midrib visible only near base. Large elongated internal cells surrounded by small, irregular, coloured cells.
Habitat: On rocks, lower intertidal pools and subtidal, perennial, a northern species abundant in Scotland, north of England, north and west Ireland south to Achill Island, but uncommon in Donegal, Leitrim, and Sligo.