Butterfield Bank shares were the heaviest traded on the Bermuda Stock Exchange last week.Some 12,100 of the Bank’s shares changed hands, closing down 3 cents at $1.15.Butterfield Preference shares also traded, closing unchanged at $1,235.00 on a volume of 80.Argus Group saw 700 of its shares trade to finish the week up 4 cents at $4.20.Overall the BSX was off 1.29 percent, or 13.50, for the week, at 1,044.65 on a total trading volume of 12,800 shares.