Phylum: Ochrophyta   Family: Fucaceae

Pelvetia canaliculata (Linnaeus) Decaisne & Thuret, 1845

Channelled Wrack

A seaweed of the upper shore. The name is derived from the curled frond that forms a 'channel'. Reproductive bodies are elongate and appear at the tip of the dichotomously branched fronds

References: 
Fish & Fish (2011) - A Student's Guide to the Seashore;
Bunker, et al - Seaweeds of Britain and Ireland