NEW YORK, Feb. 28, 2012 /PRNewswire/ -- Alleghany Corp. (NYSE:Y) will replace Transatlantic Holdings, Inc. (NYSE:TRH) in the S&P MidCap 400 index after the close of trading on Monday, March 5.  Alleghany is acquiring Transatlantic Holdings in a deal expected to be completed before the opening of trading on March 6 pending final approvals.

Alleghany offers specialty insurance and reinsurance. Headquartered in New York, NY, the company will be added to the S&P MidCap 400 GICS Reinsurance Sub-Industry index.

Following is a summary of the change:

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SOURCE Standard & Poor's