Mid eulittoral exposed to moderately exposed bedrock, often with nearby sediment, covered by a dense band or large patches of the mussel Mytilus edulis. The community often supports scattered Fucus vesiculosus and occasional foliose red seaweeds such as Porphyra umbilicalis, Osmundea pinnatifida, Mastocarpus stellatus, Palmaria palmata or the calcareous algae Corallina officinalis . The ephemeral green seaweeds Enteromorpha intestinalis and Ulva lactuca commonly occur on the shells of the mussels. The barnacle Semibalanus balanoides is common on both the mussel valves and on patches of bare rock, where the limpet Patella vulgata also can be found. The whelk Nucella lapillus and the winkle Littorina littorea can be found within the mussel bed. Situation: Above this biotope is a M. edulis and S. balanoides dominated biotope (unit A1.113) or a F. vesiculosus dominated biotope (unit A1.213). In the lower eulittoral zone below A1.221 is a biotope dominated by the wrack Fucus serratus, M. edulis and a higher diversity of red seaweeds (units A1.222; A1.2141).