AKICIBF: Whelks?

WTF is a whelk, anyway? No, let me rephrase. What are whelks in the context of selling them in England at roadside attractions not particularly near the sea? A whelk is, as far as I know, a sea mollusk with a rather prettily shaped shell -- are they sold in the shell, raw, cooked, empty shells only, or what? Are they meant to be a snack, a souvenir, or raw provender? Is this the quaint English equivalent of boiled peanut stands in North Georgia?

Yours sincerely,

Confurzled