I received an e-mail from an Internet visitor named Erik here in Louisville, Kentucky asking if I could identify this fossil his son found in a creek. Luckily, I had seen this type of fossil before and happily responded with some information about it. Erik was nice enough to let me post the pictures to share the find with others here on the Internet.
Since it was found in a creek it is harder to determine exactly what limestone layer it is from. More than likely it is a Devonian Period fossil and is of the genus Hippocardia. The fossil creature looks mostly intact and is of good size and detail. A very nice find!
UPDATE (2/2024): This fossil is probably Hippocardia cuneus (Conrad, 1840) from the Middle Devonian Period of the Jeffersonville Limestone.