Nick Compton was dismissed for 166 as Somerset extended their first-innings total to 458 on the second day of the LV= County Championship match with Durham at Taunton.
Resuming on 139, the England opener had batted for seven hours when he edged a catch behind off young off-spinner Ryan Buckley, who finished with 3-128.
Peter Trego, George Dockrell and Jamie Overton provided valuable support with 42, 31 and 24 respectively.
Durham replied with 163 for three, Scott Borthwick making 56 and Mark Stoneman an unbeaten 78.
Somerset began the day on 336 for five off 98 overs, with 12 more to get to the 400 mark and claim maximum batting bonus points.
They only managed to reach 379 by the end of the 110th over as Compton, in particular, declined to change tempo from the first day.
He faced 324 balls and hit 18 fours and a six before being surprised by a bit of lift from Buckley and edging through to Phil Mustard, with the ball sticking between the wicketkeeper’s legs.
That made it 390 for six and with only five more added Trego, unbeaten on 14 overnight, became another victim for Buckley, well-caught by Paul Collingwood at slip after edging the ball over Mustard's head.
Craig Meschede made only 12 before being caught behind off Mark Wood, who showed a lot of heart in the conditions to claim 2-89 from 29 overs.
It was 432 for eight at lunch, after which Overton was caught at point off Borthwick, who followed up next ball by dismissing Dockrell for his highest score for Somerset.
The promising Overton, pictured right, made the breakthrough when Durham replied, having Keaton Jennings picked up by James Hildreth in the slips for 15 with the total on 38.
However, Stoneman breezed to his half-century off just 53 balls, with 11 fours, and found an equally aggressive partner in Borthwick.
He followed his partner to fifty, from 57 deliveries, and it was a surprise when Borthwick was caught at short cover off Dockrell to reward the left-arm spinner for changing to the Old Pavilion End.
There was a bonus for Somerset off the last ball of the day as Will Smith, on seven, carelessly drove Overton straight to Gemaal Hussain at mid-off, who held a waist-high catch.