CBOE Holdings (CBOE) is up $1.46 to $27.93 and near session highs on share volume of 2.6 million, which is almost 10X the typical levels through midday, after S&P selected the stock to join the MidCap 400 Index. CBOE reported earnings yesterday morning and edged up 17 cents on the results. The company is also presenting at a Credit Suisse conference Friday. Sentiment seems decidedly bullish, as the stock is rallying and options volume is running 5.5X the daily average. 11,000 calls and 3,460 puts traded on the owner of the Chicago Board Options Exchange so far. The action has been small sizes. The top trade is a 258-lot of Feb 28 puts for 45 cents. Sep 28 calls, Mar 27 puts, Feb 28 calls, Feb 27 calls and Jun 18 calls are the most actives and implied volatility is moving up 8.5 percent to 23 on the day.