Busycon contrarium is a large gastropod in the family Melongidae. The shell of the lightening whelk is usually very recognizable because it spirals toward the left instead of the right like other gastropod shells. Juvenile shells have lightning bolt shaped stripes on the shell hence the common name lightning whelk. The interior of juvenile shells can be white, yellow or pale blue. Adults, on the other hand, are gray with a few vertical violet-brown streaks (Magalhaes 1948). The aperature of the adult shells can vary from white, pale yellow to orange or bright red.