Identify this seafood from the Black Sea known in Romanian as “rapane”?

Question

Here on the Black Sea in Romania people are eating a shellfish called in Romanian "rapane" which they translate as "oyster" when I ask.

But they are elongated spiral shells which to me look nothing like the chunky flattish oyster shells in Australia. Besides which there is another Romanian word "stridie" for oyster and I can't find "rapane" in my print dictionary or any online dictionary. One person told me these are "sea oysters" as opposed to "ocean oysters". I've also been told they're not a native local species.

Here are some photos of a dead rapane shell on the beach. I'll replace them with better photos when I can take some:

Answer

They look like a species of whelk, which is a catch-all term for sea-snails. See the Wikipedia article here.

Check more discussion of this question.