See if these small files tell you enough. I can send the full size file if you need them. They were washed onto the cobble bar about 100 yards above our pavilion site on Whites Creek. They were very fresh with remnants of flesh still attached. I suspect some lucky bird found his dinner right before we go there.
Those are Villosa vanuxemensis, Mountain Creekshell. A few years ago during a fundraiser at your creek for CFI, Peggy Shute found a live individual of this species near on your place, and it was the first record for Whites Creek. We put it back and I made a note that the species was found there, and was hoping someday to come back and look some more because there could be other species there. Any chance you could donate these shells to the UT mollusk collection?
By the way, one of those is female the other is male.