** Irish insurer's shares down 5.7 pct at $33; amongtop losers on the New York Stock Exchange
** XL in talks to buy Bermuda-based insurer Catlin Group Ltd
** XL's possible cash-and-stock offer values Catlin at 699pence per share, a 20 pct premium to stock's Tuesday close
** Catlin's shares rise as much as 17 pct to a record highof 679.50 pence on the London Stock Exchange
** Catlin was top gainer on London's FTSE-250 Midcap Index