The Nasdaq Stock Market Inc. announced today that it has completed its acquisition of the INET ECN.

Back in April Nasdaq agreed to acquire Instinet Group Inc. and sell Instinet’s institutional broker division to private equity firm Silver Lake Partners. The deal came in response to the NYSE’s proposed acquisition of Archipelago Holdings Inc., which was formally approved by shareholders and seatholders earlier this week.

In connection with the closing of Nasdaq’s acquisition of Instinet, Instinet’s stockholders will receive approximately US$5.0881 per share. In August of this year, Instinet stockholders were also paid a dividend of 32¢ per common share, based upon the net after-tax proceeds of Instinet’s sale of Lynch, Jones & Ryan Inc. As a result of these transactions, Nasdaq now owns INET ECN, the electronic trading system.

The firm says that the completion of INET acquisition provides Nasdaq with a technologically superior trading platform and enhances Nasdaq’s ability to compete with U.S. and international market centers. Nasdaq also expects to realize significant savings as a result of INET technology. Investors will benefit from increased limit order interaction, improved quality of execution, increased speed and a low-cost trading platform.

Bob Greifeld, president and chief executive officer of Nasdaq, said, “This transaction is a key part of Nasdaq’s growth plan to provide the most liquid and efficient market for global equities, and to be the number one market for trading stocks. With increased order interaction in both Nasdaq and exchange-listed securities — combined with a rising understanding among public companies about the importance of market quality — we will also improve our ability to attractlistings.”

“Silver Lake Partners’ acquisition of Instinet Group’s Value Added Brokerage was pivotal in making this step possible. We would like to thank them and all of our partners including Hellman & Friedman LLC, JP Morgan, and Merrill Lynch, for their efforts in completing the transaction,” he added.