Art in Shell of the Ancient Americans: Second Annual Report of the Bureau of Ethnology to the Secretary of the Smithsonian Institution, 1880-81

Some writers have suggested that the ancient peoples of the interior districts must have held shells from the sea in especial esteem, not only on account of their rarity, but also by reason of some sacred properties that had, from the mystery of their origin, become attached to them. It would appear, however, that shells were valued chiefly for their utility and beauty, and that fresh water as well as marine varieties were constantly employed. In their unworked state, for their beauty alone, they are treasured by peoples in all grades of culture, from the savage up through the barbarian stages to the most civilized state. As they are most conveniently shaped for utensils and implements, they have been of great service in the arts, and were thus of the greatest importance to primitive peoples.

It must not be supposed that the natural shells found in graves were always destined for use in an unworked state, but they should doubtless in many cases be regarded as highly-valued raw material intended for use in the manufacture of articles of utility and taste, in the tempering of potter's clay, or in effecting exchanges with neighboring tribes.