The Cincinnati Bengals continued to raid the San Francisco 49ers defense on Monday when the Bengals acquired safety Taylor Mays  for an undisclosed draft pick.  Mays becomes the third key member of the 49ers defense to join the  Bengals this season, after cornerback Nate Clements and linebacker Manny  Lawson signed free-agent deals earlier this month.  Mays had been on the trading block for close to three weeks, ever since  free-agent S Donte Whitner spurned the Bengals at the last minute to  sign with the 49ers.