What you are thinking of is the bumblebee snail, Engina mendicaria, a saltwater snail that looks almost exactly like them. They have a smoother shell though. Funny enough, they are also known to kill other snails (specifically vermetids), I bought a few for that purpose but haven’t seen them do it. Still a beautiful part of the reef though (when the pistol shrimp doesn’t borrow them).I'm no mollusc expert but that looks like the kind of saltwater snail that is commonly seen in reef tanks.