Phylum: Rhodophyta   Family: Callithamniaceae

Callithamnion granulatum (Ducluzeau) C.Agardh, 1828

A small epiphyte, easily overlooked. It grows on Corallina spp. and on molluscs and bedrock in lower intertidal pools

References: 
Maggs & Hommersand (1993) - Seaweeds of the British Isles, Volume 1 Rhodophyta, Part 3A Ceramiales