worn shells from SC I can't identify

[rhclouser]

These shells were found in North Myrtle Beach SC. They're quite worn, and all have taxodont dentition. I think they're some kind of ark shells, but they all look a little different than the ones I'm sure of. If I number them from top left to lower right,

1 2 3
4 5 6

I think 3 and 6 (and maybe 1) are blood arks, but look a little different from the others I have and am sure of.

But I'm not sure about the others. The beak/umbo are near the center of the hinge line. 1 and 4 might be ponderous arks.

I guess my real problems is with 2 and 5.

Any help from anybody would be greatly appreciated.

Thanks,
Bob