The inventor of the present invention has discovered that it would be advantageous to provide an improved system for retaining or otherwise mounting a flexible, resilient valve defining an initially closed orifice which can be opened to accommodate fluid flow through the valve, wherein the design of the system could provide advantages not heretofore contemplated in the industry or suggested by the prior art. In particular, the system of the present invention facilitates proper closing of the valve after portions of the valve have been forced away from their initially closed configuration.