The choice of N. gibbosulus in Mediterranean sites and N. kraussianus is South African sites is usually a functionality in their availability inside the vicinity from the sites, but would not explain why this genus was preferred more than other shells of similar dimension and shape. A comparison in the https://medium.com/@spoilmevintagediy/the-rich-history-of-beadwork-a-journey-through-the-ages-4e4fd2e474cf