NEW YORK, Aug. 14, 2014 /PRNewswire/ -- S&P MidCap 400 constituent Mallinckrodt plc (NYSE:MNK) will replace Rowan Companies plc (NYSE:RDC) in the S&P 500, Rowan will replace Mallinckrodt in the S&P MidCap 400, and GulfMark Offshore Inc. (NYSE:GLF) will replace Questcor Pharmaceuticals Inc.  (NASD:QCOR) in the S&P SmallCap 600 after the close of trading on Monday, August 18. Mallinckrodt is acquiring Questcor Pharmaceuticals in a deal expected to be completed tonight.

Mallinckrodt develops, manufactures, markets, and distributes branded and generic specialty pharmaceuticals, active pharmaceutical ingredients, and diagnostic imaging agents. Headquartered in Dublin, Ireland, the company will be added to the S&P 500 GICS (Global Industry Classification) Pharmaceuticals Sub-Industry index.

Rowan Companies provides offshore oil and gas contract drilling services. Headquartered in Houston, TX, the company will be added to the S&P MidCap 400 GICS Oil & Gas Drilling Sub-Industry index.

GulfMark Offshore provides offshore marine support and transportation services. Headquartered in Houston, TX, the company will be added to the S&P SmallCap 600 GICS Oil & Gas Equipment & Services Sub-Industry index.

Following is a summary of the changes:

Additions to and deletions from S&P Dow Jones Indices do not in any way reflect an opinion on the investment merits of the companies involved.

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