Elachista fucicola (Velley) Areschoug
Description: Thallus a loose, globose cushion to 14 mm wide from which a tuft of free assimilatory filaments arises. Assimilatory filaments unbranched, usually more than 100 µm wide and10 –20 mm long, coalescing basally together with paraphysis-like filaments into a loose cushion; cortex and medulla present in the cushion. Many discoid chloroplasts in each cell. Unilocular sporangia sunken in the cushion; plurilocular sporangia unknown.
Habitat: mid to lower intertidal and shallow subtidal; epiphytic on Fucus species, including F. vesiculosus (above). Widely distributed in Ireland and Britain; common.