This apotropaic amulet intended to prevent snake bites and possibly to refresh the throat of the deceased1. They are mainly in red carnelian and jasper, but faience and gold were also used1. Period: New Kingdom onwards but mainly from the Late Period with a variant in which the head of the snake forms an angle with the body (see below)
References
1Andrews C. Amulets of Ancient Egypt, 1994, p. 85 and Figs. 86a-e





