This interesting fossil is some sort of clam preserved by carbonaceous film. It was found in the Lexington Limestone of Franklin County, Kentucky. The name might be a Psiloconcha sp. If you look at the picture of the matrix plate, it was fossilized in place with a number of other sea creatures. In addition, a brachiopod imprint appears in the matrix as well. Also the clam might have some calcite crystals at one end of it.
Thanks to Lawrence for these fossils.
