Shares in the National Bank of Greece and Eurobank plunged by 30 percent in early trading on the Athens stock exchange on Monday, following a suspension of their plans to merge. The Athex index of leading shares was down by 1.69 percent at 809 points shortly after opening, with a sub-index of banking stocks off by 16.67 percent, after the Greek central bank said late Sunday that the four biggest banks in the country would be recapitalised separately.