Freshwater pearl mussel - <p><i><a href="//commons.wikimedia.org/w/index.php?title=Margaritifera&amp;action=edit&amp;redlink=1" class="new" title="Margaritifera (page does not exist)">Margaritifera</a></i>, double valved specimen, outside, length 108 mm.; Teisnach, Germany, 1964 </p> © Tom Meijer - CC-BY-SA-3.0 - Wikimedia Commons