Phylum: Rhodophyta   Family: Corallinaceae

Corallina officinalis  Linnaeus, 1758

Coral Weed

Probably the most characteristic seaweed of the middle shore, most likely found in shallow rock-pools. A red seaweed that can look brown in brightly lit areas causing pigment degradation. It feels stiff because of calcified tissue

References: 
Fish & Fish (2011) - A Student's Guide to the Seashore;
Bunker, Brodie, Maggs & Bunker (2017) - Seaweeds of Britain and Ireland;
Hiscock (1986) - A Field Key to the British Red Seaweeds