OK Kevin,
Your posting was like a shell tornado! There is a scene in a James Bond
movie where a Bond Beauty collects shells from the surf (to sell at a profit).
Another is an Hawaii 5-0 where someone is concealing a textile cone under a
tray...to do someone else away with.
There are no shelling sites in Maryland per se, unless you like the Littorna
snails, picked off sedges. I have found some large fresh water clams at
Myrtle Grove Nature Reserve. I collected many beached Epitoniums at Cove
Point, as a kid. Also many broken and fossilized (and sub fossil) shells from
the crumbling cliffs. I suspect that there aren't any recent large univalves
living in the Chesapeake Bay.
Hope you get more responses, Sincerely, Matt