The structure indicated is the eponychium of the fingernail.

The eponychium is a thickened layer of skin which surrounds the nails of the fingers and toes. It serves to protect the area between the nail and the epidermis from infection. The eponychium is often confused with the cuticle. The cuticle is the visible fold of dead skin that forms a semi-circular shape on the proximal nail plate, and it is this layer of dead skin that is removed during a manicure. The eponychium is the living fold of skin which produces the cuticle.