Favoritos de amr_mn

Large, permanent lake. Sandy mud bottom.
Image 1 shows outer view of right valve. Large at 18.2mm length. Beak a little anterior of centre. Striae coarse and more-or-less evenly spaced.
Image 2 shows inner view of left valve. Both dorsal and ventral margins relatively long. The meeting of the dorsal margin with the anterior and posterior ends is less angular than in some specimens.
Image 3 shows the dorsal view. Anterior to right.
Image 4 shows the anterior view, with beaks raised above the dorsal margin.
Image 5 shows a ventral view of the left valve, with cusps of posterior (left) and anterior (right) lateral teeth.
Image 6 shows the foot and siphons.

Found relatively long-dead below the Kost Dam among hundreds of O. ligamentina shells and dozens from other species.

Both valves, still attached.

At 455g, this is the heaviest shell I've collected from any Unionid species (all collections in Minnesota).