Phylum: Rhodophyta   Family: Bangiaceae

Porphyra umbilicalis Kützing, 1843

Tough Laver

Usually on bedrock but also as an epiphyte. Common

References: 
Brodie & Irvine (2003)- Seaweeds of the British Isles, Volume 1 Rhodophyta, Part 3B Bangiophycidae;
Bunker, Brodie, Maggs & Bunker (2017) - Seaweeds of Britain and Ireland