Commonly used as an examplar of it’s family, this fresh water mussel has a wide range across the whole of northern europe from the British Isles across to Siberia and down to Northern Africa. There are many synonyms for this one species. The top diagram shows the musculature of the mussel including the anterior and posterior adductor muscles used to keep the valves together (A.Ad & P.Ad), retractor muscles used to retract the foot (A.R & P.R) and the foot protractor muscle (Pr). The middle diagram is of the scarring from muscles left behind in a shell once the soft tissue has been removed. The bottom diagram focuses on the dorsal edge of the mussel to show the pericardium (Pc) a clear window which reveals the heart (Au & V) and the Keber’s organ, also known as the Organ of Bojanus (O.Bj).