Here is a clam I found at Speed Quarry, Indiana back in April. Until a few days ago I did not know its scientific name until I came across an Indiana Geological Annual Report for 1900. It had a section on Devonian fossils and this was pictured on one of the plates.
This clam or pelecypod is called Paracyclas lirata.
I will update this section later with a image with a scale to show how big this clam was. Also I believe I have found 2-3 of these species.
Another thing I recently learned is that the Jeffersonville limestone layer found here locally is very similar to the Columbus limestone layer found in Ohio. Since we have to refer to Ohio fossil bulletins from the State of Ohio Department of Natural Resources Division of Geological Survey it is good to know. Referring to their Bulletin 54 from 1955, they comment that the genus Paracyclas could be called "round clam". It also refers to a species of clam called Paracyclas elliptica that occurs in Columbus, Deleware, and Prout layers.