It appears to be a Colus Ventricosus, otherwise known as a Stout Colus. The description in the only shell book I have that lists this shell (A Field Guide to the Shells of Our Atlantic and Gulf Coasts by Percy A. Morris) says it is a "deep-water form, found off the coast of northern Maine."
I am wondering if any of our readers can tell me if I am correct. Because of the confluence of the Gulf Stream and the Labrador Current we sometimes find shells that are more common in distant waters.
Our latest Ocracoke Newsletter is the story Alice and Theodore Rondthaler of Ocracoke. You can read it here: http://www.villagecraftsmen.com/news032112.htm.