Shell money most valued by the Native American tribes of the Pacific Coast from Alaska to northwest California was "Dentalium shell", a species of long narrow marine shelled mollusk, a tusk shell or scaphopod. The tusk shell is naturally open at both ends, and can easily be strung on a thread. This shell money was valued by its length rather than the exact number of shells; the "ligua", the highest denomination in their currency, was a length of about 6 inches. Farther south, in central California and southern California, the shell of the olive snail "Olivella biplicata" was used to make beads
Prayer beads beads and have no religious purpose) has an odd number of beads—usually one more than a multiple of four, e.g. (4x4)+1, (5x4)+1. Since the beads are fingered in an automatic manner, they allow the user to keep track of how many prayers have been said with a minimal amount of conscious effort, which in turn allows greater attention to be paid to the prayers themselves. A fresco picture dating from 1600 B.C., recently discovered in Akrotiri of Santorini (ancient Thira), shows women handling a prayer rope of beads. The Desert Fathers of the 3rd to 5th centuries, used pebbles or