The cerata rarely have iridescence. If the Mediterranean F. vicina is shown by DNA to be present in N.W. Europe, this specimen could be one, though lack of white line down front of cerata is against that. . Ref. https://academic.oup.com/mollus/article/86/1/64/5766684?login=false . Dorsal hump is over the pericardium. S. Norway. April 2020. © E. Svenson.