Your fossil could be a brachiopod or mollusc. Brachiopods were common in the past (only a few species survive today) and are often found as fossils. Mollusc fossils can be bivalves like clams and freshwater mussels, or single shells like snails and many sea-dwelling creatures. Most mollusc fossils are the remains of marine or freshwater animals as the preservation of land molluscs (snails etc.) is far less common. Mollusc fossils can be found in the Carboniferous coal measure rocks (about 300 million years old) of the Potteries area.
If you want to try and identify your brachiopod or mollusc fossil more precisely, you could search the Virtual Store or could take it to your local museum to be identified.
Click here to search the Virtual Store.