Editing Tusk shell (section)

===Shells===
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|image1=Antalis inaequicostata 01.JPG
|caption1=Shell of ''[[Antalis|Antalis inaequicostata]]''

|image2=Dentalium octangulatum 01.JPG
|caption2=Shell of ''[[Dentalium (genus)|Dentalium octangulatum]]''

}}
The shells of the members of the Gadilida are usually glassy-smooth and narrow, with a reduced aperture. This along with other structures of their anatomy allows them to move with surprising speed through loose sediment to escape potential bottom-dwelling predators.

The Dentalids, by contrast, tend to have strongly ribbed and rough shells. When they sense vibrations anywhere around them, their defensive response is to freeze. This makes them harder to detect by animals such as [[ratfish]], which can sense the electrical signals given off by the most minute muscle movement.