Phylum: Rhodophyta   Family: Polyideaceae

Polyides rotunda (Hudson) Gaillon, 1828

Discoid Fork Weed

Similar to Furcellaria lumbricalis but with richer colouring and a discoid holdfast. Common attached to rocks in the mid to lower intertidal zone

References: 
Bunker, Brodie, Maggs & Bunker (2017) - Seaweeds of Britain and Ireland;
Hiscock (1986) - A Field Key to the British Red Seaweeds