There are thirteen large segments which represent the thirteen moons which make up the lunar year. By counting the smaller segments around the lower edge of the shell, you will find there are 28, which represents the 28 days between new moons.
Every group of Native Americans has names for the thirteen moons and there are stories to go with each new moon. The names of the moons and the stories that accompany them vary from one group to another, but each is descriptive of the season in which the new moon appears.
The Human Body carries the same calendar as follows:
2 shoulder, 2 elbow, 2 wrist joints = 6
2 hip, 2 knees, 2 ankle joints = 6
universal neck joint= 1