Cowrie (kadi) a glossy brightly marked marine shell, mostly of Maldives origin, extensively used as coin in Bengal up to the end of the eighteenth century and sparingly down to the end of the nineteenth. In ancient and medieval times cowrie (Cypraeamoneta- money cowrie), was used as a medium of transaction, mostly in South Asia and Africa, though it was not unknown to other parts of the world including China and Europe. The term was the same everywhere, but it also had local names. In sanskrit it was called kapardak. As words signifying money, kapardaka and cowrie are in use in Bangla even today.
The mangalkavya, a medieval collection of verses of Bangla literature, is replete with references to the use of cowrie as money. Silver coins were used in large trading centres of import and export and not in remote villages where the cowrie was the most convenient medium of exchange.
In the works of medieval historians like Masudi and Abul Fazl, there are references to the market value of commodities in terms of cowrie. That the process of monetisation of land revenue collection was begun with the cowrie is evidenced by the jamabandi of Mughal revenue settlements. The raiyats were free to pay revenue in cowrie. In frontier districts such as rangpur and sylhet, the raiyats paid their rent to zamindars mainly in cowrie as late as the early nineteenth century.
Of the cowrie currency, the most interesting aspect was its counting system, which continued unchanged until the end of its use as a medium of exchange. The counting went like this: 4 cowries make a gonda, 5 gondas a budi, 4 budis a pan, 16 pans a kahan and 10 kahans a rupee (a silver coin of approximately 172 grains). Another variant of the same counting system was: 4 cowries make a gonda, 20 gondas a pan, 4 pans an anna, 4 annas a kahan and 4 kahans a rupee (28,880 cowries). At one time, the maritime countries of Europe imported cowries, but it was not for use as currencies but for buying slaves from the African market, where the cowrie was the only medium of exchange. [Sirajul Islam]