Together, the eponychium and the cuticle form a protective seal. The cuticle is the semi-circular layer of almost invisible dead skin cells that "ride out on" and cover the back of the visible nail plate while the eponychium is the fold of skin cells that produces the cuticle. They are continuous, and some references view them as one entity; in this classification, the names "eponychium", "cuticle", and "perionychium" are synonymous. It is the cuticle (nonliving part) that is removed during a manicure, but the eponychium (living part) should not be touched due to risk of infection. The eponychium is a small band of living cells (epithelium) that extends from the posterior nail wall onto the base of the nail. The eponychium is "the end" of the proximal fold that folds back upon itself to shed an epidermal layer of skin onto the newly formed nail plate. The perionyx is the projecting edge of the eponychium covering the proximal strip of the lunula.