XY-Dragon Cannon

"X-Head Cannon" + "Y-Dragon Head" This card cannot be Special Summoned except by removing from play the above cards on your side of the field; then you can Special Summon this card from your Fusion Deck ( You do not use "Polymerization"). Discard 1 card from your hand to destroy 1 face-up Spell or Trap Card on your opponent's side of the field.