In the countries on the coast, the shells were fastened together in strings of forty or one-hundred each, so that fifty or twenty strings represented a dollar; but in the interior they were laboriously counted one by one, or, if the traders were expert, five by five. The districts mentioned above received their supply of kurdi, as they were called, from the west coast; but the regions to the north of Unyamwezi, where they were in use under the name of simbi, were dependent on Muslim traders from Zanzibar. The shells were used in the remoter parts of Africa until the early 20th century, but then gave way to modern currencies.