Spiral Shaped Fossils
Each of the three represented classes of Phylum Mollusca includes organisms with a spiral shape. Examples include - cephalopods (like present day nautilus), gastropods (like present day snails), and bivalves (clams and oysters). Examine the fossil and pick either a shell with a flat plane of growth at the center, or one that budges out in the center, or one with a "curly" looking tail.