The following pictures show an Ordovician period clam called Caritodens demissa. This clam was found in eastern Jefferson County, Kentucky (just outside of Louisville, Kentucky). It was found in the Grant Lake Formation.
Part of clam is still embedded in the rock matrix. The fossil is about 4 cm wide and 3.5 cm long.
The Fossils of Ohio book says on page 139 this clam is common. It describes it as "a large species distinguished by auricles (large winglike extensions of the hinge), strongly developed comarginal ridges, and the lack of any radial ornamentation." A picture can be found in the book at Figure 12-1.1.
Here is a link to another fossil found on the KYANA Geological Society website. This might be one at this link at the Kentucky Paleontological Society website. This link on the Dry Dredgers website shows a number of Caritoden pelecypods they have found