Scaphopoda
Scaphopoda, also known as tusk shells or tooth shells, are a class of marine Molluscs with worldwide distribution, and are the only class of molluscs that is exclusively infaunal (living in marine sediment). There are approximately 500 living species within the class ranging in length from 50mm to 180mm.
About Scaphopoda
Because of their subtidal habitat and the small size of most species, their shells are not as common or as easily visible in the beach drift as the shells of Gastropoda and Bivalvia.
The shells are usually glassy-smooth or strongly ribbed. Shells of Scaphopoda are not popular with shell collectors.
Scaphopoda are the most recent class of molluscs to appear in the fossil record, dating at least from the Mississippian Carboniferous, approximately 360 million years ago.