Butterfield Bank shares slid 2.7 percent yesterday, weighing on The Royal Gazette / Bermuda Stock Exchange Index.The index slumped 18.09 points, or 1.47 percent, to close on 1,216.44.Butterfield tumbled four cents to close the day on $1.46 as 1,100 shares traded. The bank’s preference shares also traded, dipping $5, or 0.4 percent, to close on $1,230, as three shares changed hands.The only domestic board company to advance was insurer BF&M Ltd, which gained 15 cents, or one percent, to close on $14.90, as 14,800 shares were exchanged.KeyTech Ltd was the most actively traded issue, with 28,416 of the telecommunication group’s shares trading, but its share price remained unchanged on $5.45.