The term 'spiral-shelled creature' can refer to two different creatures: a SNAIL and a nautilus. A SNAIL is a small mollusk with a soft, slimy body and a spiral shell. It moves slowly by gliding along on its muscular foot. The nautilus is a cephalopod mollusk with a coiled external shell and tentacles. It is found in the deep ocean and is considered a living fossil, as it has remained unchanged for millions of years.