A while back I collected a group of bivalves from the Frontier Formation (Cretaceous) just south of Kemmerer (Lincoln County) Wyoming and I am having some trouble pinning down an ID. The formation is known for containing Crassostrea soleniscus and Inoceramus, but these are neither of those. Based on my Texas Cretaceous Bivalves book, they could be some species of Panopea but I am not at all certain of that. Unfortunately, although I have quite a number of samples, there aren't any that expose the dentition so that is a bit of a disadvantage. I'm hoping one of our Wyoming experts and/or bivalve experts have seen these before as I'm pretty sure they are not uncommon. My internet searches have failed me so far. Or if anyone can suggest a good literature source for Wyoming Cretaceous bivalves, I am happy to to do some reading and deciphering. Thanks very much for any help you can provide. The first two pictures are two views of the same specimen, the third picture is a seperate one.