Abstract: A cassette and a cassette receptacle assembly are provided for use in an ocular surgical system. The cassette includes a housing which defines an arcuate race. A flexible tube extends across the race and conveys a fluid when compressed by the rollers of a roller pump. A slot is defined by the housing at the point where the tube forms a bend prior to entering the race. The slot has a height which is preferably smaller than the diameter of the tube and therefore prevents the tube from flattening as the rollers urge it away from the slot. The cassette mounting assembly includes a pair of cams which urge the cassette into a locked position with respect to the roller pump.