Operculums are also known as Cat's Eye Sea Shells or Trap Doors. The trap door is the part of the shell that the mollusk pulls in to seal itself inside its shell to protect against predators. The cat's eye is found in various kinds of seashells but the most well known comes from the turbo or turban family. Color varies from green to red or white depending on the particular type of turbo shell. The most popular is the green cat's eye which comes from the beautiful tapestry turban (Turbo petholatus).