Side cutters are a handy tool for cutting some kinds of seashells.  We use them for tubular shaped shells like tusks and urchin spines.  You can purchase side cutters from us on our Tools page. 

Grasp the shell in the jaws of the cutter with the large end of the shell outside of the flat side of the jaws.  Hold the large end of the shell with one hand and make the cut.  Use a box or plastic bag to catch the cut pieces as they "fly" off the cutter. 

Because seashells are brittle, the cut ends will be jagged.

Place a sheet of sandpaper (180 grit is good) on a flat surface and drag the ends of the cut pieces across the sandpaper to make them smooth.  

Cut tusk shells provide the background for the ring of flowers in the Sailors Valentine shown below