Okay, so I've been collecting down by my creek in Oldham Kentucky. I have found plentiful brachiopods and corals, as well as the occasional gastropod. I have not seen any crinoids in the area. Here is a high-spired gastropod as well as some (Orothid? Rhynchonellid? Spirifer?) Brachiopods I recently picked up.
The fossil in question that I need to identify is about an inch long. It's cross-section appears to have the shape of a wing, with an edge on each side and a curve in he middle. External lines stretch from edge to edge. (photos coming)
I note that the shape seems to taper off in the direction perpendicular to the lines going across the curves.