Anal sulcus

It houses the anal siphon through which the snail expels water and waste products.

The anal sulcus can be described, according to the species, as well-defined, weakly defined, shallow, sharp, wide, narrow or inverted U-shaped.

In some species, such as in the Murex family, the anal sulcus is absent.

The anal sulcus can be linked on the edges to a fasciole, a spiral band on the shell, formed by successive growth lines.

It can also have a subsutural callus (such as in Clathrodrillia callianira).