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