Lynn Ingram writes that she thought she'd found the state seashell of North Carolina, a Scotch bonnet, on one of the state's beaches. But she soon discovered that the shell was a species of sea snail that is only found in the Pacific Ocean. How did it end up in the Atlantic? Joseph Montoya, professor in the School of Biological Sciences who is also director of Georgia Tech's Ocean Science and Engineering program, says one possibility involves ballast tanks of oceangoing ships; sometimes these shells start as larvae living in plankton that may have been caught up in a ship's ballast water.