It almost looks like you may be able to bend the rails with a little persausion you could get the gap to fit but I've never done that to a saddle so I only reccommend that if you take the liablility
Otherwise I believe the safe thing to do is take back the saddle, or bike and saddle or seatpost and saddle to where you bought it, if purchased online then to the lbs. and don't forget your reciept should you need to do a return.