I have several cowries shells of various sizes and species in my bone sets. As shells go they are ideal for bone sets. Their fragile edges are shielded so they don’t chip easily. They are not prone to thin spots so they are less likely to break. They have two obvious faces. They are round for the most part and smooth making them less likely to injure other pieces in the set. They feel good in the hand if you throw that way. And they are beautiful. Some bone sets come with a cowrie shell. Some sets provide a suggested meaning but you can have them mean anything you want. I mostly use them to represent people in my set. Because of the wide variety of sizes and colors they are ideal for this purpose. Smaller ones can be children, larger ones adults, larger still can be ancestors, etc. You can even break them down into male and female by using different sized pieces from the same species. In my travel set I have various cowries to represent people of various ages but I don’t differentiate them by gender. In my main set I do differentiate by gender and for ancestors by maternal and paternal lines as well. They are plentiful and readily available from many sources. If you don’t live near the shore with ubiquitous shell souvenir shops you can usually get them from your local botanica, though sizes and species may be limited. You can overcome uniformity by using paint or a marker to put distinguishing marks on the backs and around the “mouths.” If you are looking for an inexpensive, versatile addition to your bone set consider cowrie shells.
Happy Bone Reading!