Lampsilis siliquoidea, also known as the fatmucket,[1] is a species of freshwater bivalve in the family Unionidae.

The shape of the shell is oblong to elliptical, compressed or inflated, with uniform thickness.

In the parasitic glochidial stage they feed on blood from hosts species, which include bass, perch, walleye, and sturgeon.

It is widespread in North America, found in the drainages of both the Mississippi River from New York to Minnesota, the Great Lakes, and Hudson Bay.

It lives in lakes, rivers, streams and quiet waters, usually on sandy-mud bottoms.