This is a rostroconch and is probably a Hippocardia. It was found in the Louisville Limestone in Jefferson County, Kentucky. According to the Fossils of Ohio (1996) book, "Although the paleoenvironmental settings of some Silurian units in Ohio are such that rostroconchs could have been present, they have not been reported." (pages 132-133) So this fossil was found in the Silurian layer and is somewhat rare.
The rostroconch was at one time classified as a Pelecypoda but now have their own class as Rostroconchia. The section in the book only covered 4 pages so I am guessing these creatures are somewhat rare and not studied a great deal. The geologist that wrote the section was named Richard D. Hoare who was a professor at Bowling Green State University in Ohio from 1957-1990.
My cousin found this fossil and it appears he may have cleaned it with an air abrasive cleaner.