Phylum: Ochrophyta   Family: Chordariaceae

Leathesia marina (Lyngbye) Decaisne, 1842

Punctured Ball Weed

An annual species of the inter-tidal zone, attaching itself to rocks and othe algae. Quite globular in the young state but becoming increasingly irregular with age and when coalescing together

References: 
Bunker, Brodie, Maggs & Bunker (2017) - Seaweeds of Britain and Ireland