Phylum: Ochrophyta Family: Desmarestiaceae
Desmarestia aculeata (Linnaeus) J.V. Lamouroux, 1813
Desmarest's Prickly Weed; Landlady's Wig
The thallus is round, over a metre in length. The branching is irregular and flattened. Found growing on rocks in the lower intertidal zone
References:
Bunker, Brodie, Maggs & Bunker (2017) - Seaweeds of Britain and Ireland