Transatlantic Holdings (NYSE:TRH) confirmed that it has received an unsolicited proposal from Validus Holdings (NYSE:VR) to acquire all of the company’s outstanding shares of common stock.Transatlantic entered into a definitive merger agreement with Allied World Assurance Company Holdings under which the company and Allied World would combine in a merger of equals, with stockholders of Transatlantic receiving 0.88 Allied World common shares for each share of Transatlantic common stock, as previously announced on June 12.Transatlantic Holdings has a potential upside of 17.6% based on a current price of $49.02 and an average consensus analyst price target of $57.67.