23 FLUID OPERATED SUBSURFACE OIL WELL PUMPS AND PARTS THEREOF, SURFACE PUMPS FOR FURNISHING POWER FLUID UNDER PRESSURE AND PARTS THEREOF, PERFORATED CASINGS FOR LINING OIL WELL BORES, TUBING SLIPS FOR SUPPORTING OIL WELL EQUIPMENT WITHIN THE WELL, AND TUBING CLAMPS FOR SECURING TOGETHER A PLURALITY OF OIL WELL TUBINGS