These shells were an ancient money used not just in Africa, but throughout the world, predating the use of coins or in some instances used in the same economy as metal coins. Imported from the Maldive Islands in the Indian Ocean, these polished, olive-sized shells served for small everyday transactions and, gathered together in the millions, for bridewealth (a groom's gift to the family of the bride) and other major purchases and gifts. In the 18th century, one could purchase a cow for 2,500 shells, a goat for 500 shells and a chicken for 25 shells. The shells were counted and measured in many different combinations, but the most typical in some parts of Africa was the rotl, a string consisting of 32 shells, which was then aggregated in strings of 5 to constitute a bunch. Ten bunches was called a head. The shells were believed to possess the power of fertility, thus ensuring their acceptance throughout the wide territories of Africa.