Dynamic seal arrangement with X-shaped seal

A channel shaped elastomeric seal member including an elongate web member, and parallel laterally extending leg members at the ends of said web to be received in a channel shaped groove of a selected element having a first channel groove to receive said web and mutually parallel second channel grooves extending laterally from opposite ends of said first channel groove to receive said leg members, said first channel groove and said second channel grooves each being defined by a base and opposed spaced sides to sealably engage a channel shaped sealing surface adjacent said element where fluid pressure is selectively applied to at least one side of said seal and where said seal member, in cross section, includes a central body with first and second spaced feet extending outwardly therefrom to be received in and engage said opposite sides and said base of said first and second grooves, and third and fourth feet extending outwardly from said web and said leg members along a portion thereof to slidably engage said sealing surface wherein fluid can be applied to at least one of said third and fourth feet to urge said at least one of said third and fourth feet to sealing relation with said sealing surface.