Going through the stuff in my bucket that had dried out from my last trip, found more stuff that I can only guess what they might be. The first three are of a tiny disc with holes along the periphery. The next two are of three pieces of a flat discoid "rock", that was more fragile than i thought, looks like from something alive. Last two seem too light for bone, so I'm guessing sponges?
Probably some of you will know (penny = 0.75 inches or 19 mm in diameter):
Thanks!