A screen apparatus for processing stock flowing into a papermaking headbox which includes a cylindrical housing, a tubular screen mounted longitudinally within the housing, and inlet means for introducing a stock suspension into the housing for flow through the screen. Outlet means are provided for receiving the suspension passing through the tubular screen for delivery to the headbox. The improvement of the present invention provides a helical slot in the housing which discharges stock passing through the screen into the outlet means. Foil means mounted for rotation coaxially with the cylinder are provided which create a pressure pulsation to cause a dispersal of the fibers and aid in the screening operation.