As a comparison piece, this Schizophoria schnuri looks identical to the S. iowaensis I posted earlier. This specimen comes from the Skaly beds near Kielce in the Holy Cross Mountains of Poland. I'm not sure of the rock formation that it came from but they are dated to the Eifelian to Givetian stages of the middle Devonian.
Here is the inside of the pedicle valve of a S. schnuri. Note the cardinal process scars which once held the muscles that opened and closed the shell.