Abstract: A container closure comprising a cylindrically shaped, resilient, distortable membrane having a first terminal end fully affixed to the periphery of a first closure body providing a discharge aperture of predetermined size and a second terminal end fully affixed to a second coacting closure body coaxially disposed about the outside periphery of the first closure body and adapted for relative bi-directional rotation with respect to the first closure body. Relative counterrotational movement of the membrane terminal ends in one direction causes closure and sealing of the annular throat inherently created and disposed within the membrane while relative counterrotational movement in a second direction causes the previously closed annular throat to open.