Another brachiopod from the diverse Waldron Shale (Silurian, Wenlock epoch) is Parmorthis waldronensis. It reminds me a little bit of Pseudoatrypa reticularis of the Devonian (because of one valve being convex and the other nearly flat) and Dalmanella multisecta of the Ordovician (because of the shape of the interarea). It also has a strong resemblance to Resserella elegantula specimens that I've found in the Irondequoit limestone near Lockport, NY.
It turns out that a little research on the Fossilworks.org website (formerly Paleodb.org) shows that Parmorthis is a synonym of Resserella. So the resemblance is because they are one in the same. I will have to update the label to indicate Resserella waldronensis.