IPhone : cannot convert the expression's type '(size: @Ivalue CGSize)' to type 'GameOverScene'

I am a swift beginner. I've been trying to track the highScore in my spriteKit game. but the game wouldn't run when i try to call the GameOverScene from a different Scene, and instead it shows the error above. can anyone please help me go through this. Please see code below

override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {

   emphasized text var touch: UITouch = touches.anyObject() as UITouch

    var location = touch.locationInNode(self)

    var node = self.nodeAtPoint(location)


   // If next button is touched, start transition to second scene

    var secondScene = GameOverScene(size: self.size)

        secondScene.scaleMode = SKSceneScaleMode.AspectFill
        self.scene!.view?.presentScene(secondScene)

}

class GameOverScene:SKScene, SKPhysicsContactDelegate {

    let gameplayDict : NSDictionary = {
    let path = NSBundle.mainBundle().pathForResource("Gameplay", ofType:        "plist")
    let dict = NSDictionary(contentsOfFile: path!)
    return dict!
    }()




//Scoring variables
     var score : Int = 0 {
     didSet {
        self.setScore(score)
      }
     }


  var highScore : Int = 0 {
        didSet {
        self.setHighscore(highScore)
        NSUserDefaults.standardUserDefaults().setInteger(highScore, forKey: "highScore")
        NSUserDefaults.standardUserDefaults().synchronize()
       }
      }   

required init?(coder aDecoder: NSCoder) {

    super.init(coder: aDecoder)

    // set value of the highscore to the saved one, if any

if let high = NSUserDefaults.standardUserDefaults().objectForKey("highScore") as?

Int {
      highScore = high
    }
    }