I'm pretty sure that's not a scallop, although a broadside view of it would have been helpful. If it's a scallop, the shell shape should be almost round. It looks pretty elongated? It may be a gerontic Pteria species, maybe Pteria penguin with the wing mostly gone, but most of those are somewhat inflated, and yours looks pretty thin. It also might be one of the species of hammer oysters or tree oysters, hard to tell with a single view.
Cheers,
Don