Sri Lanka let Dinesh Chandimal reach fifty, and grew their lead to 456 before declaring their innings closed, upon the dismissal of Dilruwan Perera for 33. They hit 27 runs - Perera especially aggressive - in the five overs after tea. When he edged behind, trying to hit a short Mustafizur Rahman delivery through the offside, captain Rangana Herath brought the innings to a close. About 125 overs remained in the match.Before the tea interval, Upul Tharanga sailed to his first Test hundred on home soil, as Sri Lanka`s lead rapidly swelled. But Sri Lanka opted to bat on, despite no team having scored more than 300 in a fourth innings at this ground, and the highest successful chase being only 99.They batted like a declaration was imminent right throughout the session, hitting 160 runs at 5.16 an over, and happily burning four wickets in the pursuit of these quick runs. Bangladesh`s spinners got some real purchase for the first time in the Test. Mehedi Hasan was especially impressive, claiming two wickets under duress, and delivering a good mix of turning balls and straighter ones. Shakib Al Hasan claimed the other two scalps in the session; he had Kusal Mendis caught at the deep midwicket boundary, and bowled Asela Gunaratne with a delivery that straightened more than the batsman expected.Having been somewhat watchful in the first session, Tharanga opened his shoulders after lunch, cracking successive fours off Mustafizur Rahman and then routinely striding down the pitch to meet the spinners. He was especially severe on errors of length, creaming languid boundaries through midwicket and square leg, though he also used the cut and sweep to good effect. He used up 109 balls to reach his half century; his next 47 runs were studded with five boundaries, and came off 44 deliveries. He paused briefly on the brink of his century, then immediately began to attack again, launching Shakib Al Hasan over long-on. Two more fours were smoked off Mehedi next over, before he was bowled trying to attempt a third - Mehedi tossing the ball bravely up, and beating the batsman in the air.Gunaratne`s stay was brief and unproductive, and though Niroshan Dickwella tried plenty of expansive strokes - the reverse-sweep and paddle in particular - he only properly connected twice and mustered 15 from 17 balls. His dismissal was as much the work of the wicketkeeper as Mehedi, the bowler, Liton Das lunging to his left after Dickwella made good contact on a reverse paddle, and pouching the ball much to the batsman`s surprise and chagrin.Bangladesh were low on energy as Mushfiqur Rahim spread the field, and would drop two catches through the session. Dinesh Chandimal was reprieved at slip on 11 and would go on to see out the session on 37. Dilruwan Perera was dropped on the legside boundary on zero and went to the tea break on 19. Sri Lanka`s second-innings score was 247 for 5.An opening stand of 69 earlier in the day had helped lay the foundation for the afternoon`s attack, as Tharanga and Dimuth Karunaratne saw out the new ball with caution. Karunaratne also benefited from a dropped catch early in his innings, but could not take full advantage. He was out carelessly swatting a ball off his thighs, to the man at deep square leg, who took a good running catch.Source: espncricinfo