These fossils appear to be Volutomorpha mutabilis gastropods (named by Wade 1926). They existed during the Cretaceous Period (about 70 million years ago). This fossil was found in McNairy County, Tennessee (Coon Creek Formation).
See their identification PDF at this LINK.
Learn more about these fossils at the Coon Creek Science Center web site: http://www.memphismuseums.org/coon_creek-overview
Fossils from the Herb Miracle collection.
