NYSE Euronext (NYSE: NYX) purchased a minority stake in ACE Group Inc., a company that runs a portal through which companies can sell stocks, bonds and other securities.

Financial details of the transaction weren’t disclosed.

ACE, founded in 2010, allows broker-dealers to manage securities sales and search for offerings privately.

The acquisition comes on the heels of several other deals on the part of U.S. public exchange operators. The consolidation is said to be due to low trading volume and an increase in institutional orders that are unavailable to the public, otherwise known as dark pools. Atlanta-based IntercontinentalExchange (NYSE: ICE) is currently in the process of wrapping up its $8.2 billion merger agreement with NYSE Euronext.

On Aug. 14, private equity firms Spectrum Equity and TA Associates each acquired a minority stake in equity exchange company Bats Global Markets Inc., which separately agreed to combine with Direct Edge Holdings LLC.

In April, Forex Trader FXCM Inc. proposed a merger with online trading services provider Gain Capital Holdings Inc. Gain rejected the deal, but agreed to buy Global Futures & Forex Ltd., instead. Also in April, The Nasdaq OMX Group Inc. (Nasdaqw: NDAQ) said it would buy ESpeed, which provides trading technology, for $750 million.

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