How would I say mussel is Halal………when it toilets inside the shell……..and people eat everything together?

Well, I asked friend of mine whether mussel is Halal or Haram………but, he said Haram…..then, I asked to yahoo question…….ppls answered me that is Halal…….I am so confuse…….since,,,,,,,I never saw anybody back in Bangladesh ever to eat mussel or call it Halal…………………..Plzzzzzzz……..help me out………