Bitcoin debuts on the world's largest futures exchange, and prices fall

CME, the world's largest futures exchange, launched its own bitcoin futures contract Sunday under the ticker "BTC."

The futures fell more than 4 percent to $18,665 about two hours after opening at $20,650 and rising slightly.

The move lower was a stark contrast from the 19 percent surge in CBOE bitcoin futures during their first day of trading a week ago. The Cboe bitcoin futures, traded under the ticker "XBT," rose more than 2 percent to $18,530 Sunday evening, ET.