Tusk shells (Class Scaphopoda)

Scaphopods, or tusk shells, are a small group of burrowing, marine molluscs, which have a tubular tusk or tooth-shaped shell, open at both ends. They live buried in the sand, head downwards, with the body steeply inclined. Water enters and leaves the mantle cavity via the posterior aperture, and gas exchange takes place across the mantle cavity since gills are lacking.

The head is very reduced and lacks eyes, but is surrounded by numerous thread-like tentacles, which are used to gather small particles of food and pass them to the mouth.

Scaphopods are found mainly in the deep sea, but a few species occur in shallow water. Dentalium is quite a common species around New Zealand coasts.