Phylum: Rhodophyta   Family: Ceramiaceae

Ceramium shuttleworthianum (Kützing) Rabenhorst, 1847

One of several similar Ceramium species, which is mainly characterised by the presence of multicellular spines on the outside of each node and the strongly hooked or in-rolled apices. Found in the mid and lower littoral, attached to rocks, mussels, barnacles and limpets

References: 
Hiscock (1986) - A Field Key to the British Red Seaweeds