{TAIL ~ a hydraulic motor} operatively connected to each of {HEAD ~ said first and second screw conveyor members}; and 
{ TAIL ~ a hydraulic motor } operatively connected to each of { HEAD ~ said first and second screw conveyor members } ; and
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH