Euell Gibbons' book "Stalking the Blue-eyed Scallop" lists over 60 different
species of mollusk that he considered edible.  I would, however, take his
advice with a grain of salt.  In another of his books, he recommends milkweed
as a snack. That's pretty poisonous stuff.

I think I remember reading, somewhere, that the reason the adductor muscle is
the only part of the scallop served in the United States is that it is the
least perishable part.  In Europe, they select their foodstuffs based on
taste.  Here, the food industry is more interested in shelf life.