NEW YORK, Jan. 11, 2016 /PRNewswire/ -- S&P SmallCap 600 constituent Microsemi Corp. (NASD: MSCC) will replace Atwood Oceanics Inc. (NYSE:ATW) in the S&P MidCap 400, and Atwood Oceanics will replace Microsemi in the S&P SmallCap 600 after the close of trading on Friday, January 15. Microsemi is acquiring PMC-Sierra Inc. (NASD: PMCS) in a deal expected to be completed on or about that date pending final conditions, and the combined company's market capitalization will be more representative of the mid-cap market space. Atwood Oceanics is ranked at the bottom of the S&P MidCap 400 and has a market capitalization more representative of the small-cap market space.

Microsemi designs, manufactures, and markets analog and mixed-signal semiconductor solutions. Headquartered in Aliso Viejo, CA, the company will be added to the S&P MidCap 400 GICS (Global Industry Classification Standard) Semiconductors Sub-Industry index.

Atwood Oceanics is an offshore drilling contractor.  Headquartered in Houston, TX, the company will be added to the S&P SmallCap 600 GICS Oil & Gas Drilling 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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