function createAuction(
        address _contract,
        uint256 _tokenId,
        uint256 _startingPrice,
        uint256 _endingPrice,
        uint256 _duration,
        address _seller
    )
    external
    whenNotPaused
    {
        require(_isAddressSupportedContract(_contract));
        
        
        require(_startingPrice == uint256(uint128(_startingPrice)));
        require(_endingPrice == uint256(uint128(_endingPrice)));
        require(_duration == uint256(uint64(_duration)));

        _escrow(_contract, _seller, _tokenId);

        Auction memory auction = Auction(
            _contract,
            _seller,
            uint128(_startingPrice),
            uint128(_endingPrice),
            uint64(_duration),
            uint64(now)
        );
        _addAuction(_contract, _tokenId, auction);
    }