Phylum: Ochrophyta Family: Dictyotaceae
Dictyota dichotoma (Hudson) J.V. Lamouroux, 1809
Divided Net Weed; Brown Fan Weed
Very common in the upper to mid tidal zones, often in rock pools. Thallus flat with dichotomous branches and parallel sides, which can grow to 300 mm long but usually half that size, the rounded tips are usually divided in two
References:
Fish & Fish (2011) - A Student's Guide to the Seashore;
Bunker, et al - Seaweeds of Britain and Ireland