Leptaena is a common Strophomenid type brachiopod that ranges from the Ordovician thru the Carboniferous periods of the Paleozoic. I've written about it before in this post. The specimens below come from the Irondequoit limestone Rochester Shale which is part of the Clinton Group and is lower Silurian (Wenlockian epoch, Sheinwoodian stage) in age. I found them in a railroad cut west of Lockport, NY. The first specimen has a hitchhiker in the form of a Bryozoan.
This is a larger specimen found at the same cut but only the pedicle valve is exposed.