We later found a proper whelk: a whelk shell that contained an actual whelk critter.

Apparently some whelk are edible. Wikipedia notes "When used for cooking in the United States, busycon whelks are sometimes called scungilli, an Italian-American adaptation of the Neapolitan sconciglio which means the meat of a (usually edible) sea snail."

I just can't see me being motivated to ever try this. But never say never I suppose.

Also from Wikipedia: "whelks are scavengers and carnivores, equipped with a proboscis tipped with a file-like radula used to bore holes through the shells of barnacles, clams, crabs and lobsters. They have a large, muscular foot with which they hold their victims."