Flagstone Reinsurance Holdings SA said fourth-quarter profits slumped 77 percent to $15 million, compared to same period of 2009, as catastrophe losses took their toll.The company revealed last week that it expected Australian flood losses in December to toal around $10 million, while the triggering of aggregate covers was expected to cost a further $25 million.Net earnings for the year also fell by more than half to $97.1 million from $242.2 million in 2009.But the 'Class of 2005' Bermuda start-up, whose holding company is now in Luxembourg, managed to increase its diluted book value per share by three percent during the quarter to $15.51 and by 12.1 percent through the year.