UNITED STATES, CANADA AND MEXICO                      257 shells of some varieties, such as the common clam and the conch, were made into wampum; and that the pearls found in the shells were used as ornaments, whether lusterless pearls from the common oyster or lustrous ones from the Unio. The great shell-heaps along our coasts bear evidence that many pearls must have been found, and that, though the Spaniards who invaded the country may indeed have obtained great hoards of pearls, all of them, perhaps, were not of great value.