On the taxonomic placement of Unio ochraceus Say, 1817 in the genus Ligumia (Bivalvia : Unionidae)

Since 1975, the freshwater unionid mussel originally described as Unio ochr aceus Say, 1817, has been variously assigned to the genera Lampsilis or Lep todea. The taxonomic stability of this species has been complicated by inco mplete knowledge of certain features of its anatomy. Study of the mantle of this taxon leads to the conclusion that U. ochraceus does not belong to ei ther Lampsilis or Leptodea. The species is assigned to the genus Ligumia ac cording to established taxonomic criteria to differentiate lampsiline gener a that include characters of the anatomy and larva. The mantle edge contain s distinct, regular papillae along an uninterrupted, lamellate border and t he glochidia are of the large type.