While going through some boxes of findings from the Osgood shale I came across this Pelecypod on a large chunk of matrix. After a bit of trimming I got the piece down to a more manageable size. I think it's a Pterinea brisa based on similar specimens that Mike Popp posted on his blog at Louisville Fossils here and here.
The specimen came from the New Point Stone Co. quarry near Napoleon, IN. The Osgood shale is Silurian aged (Telychian to Sheinwoodian stage).