Aglaothamnion sepositum (Gunnerus) Maggs & HommersandAlso known as Callithamnion arbuscula (Dillwyn) Lyngbye
Description: Bushy tufts of uniseriate, dark brown-red filaments, to 200 mm high, opaque, cartilaginous, heavily corticated by rhizoidal filaments. Branched repeatedly, branches clothed with pinnate ramuli. Cells of ramuli twice as long as broad.
Habitat: Most frequently on mussels (above), but also on rocks, barnacles and limpets, mid intertidal on exposed shores, common in north, found on western coasts, less frequent on southern coasts.
Photographs © M.D. Guiry