James Hildreth top-scored with 90 as Specsavers County Championship Division One leaders Somerset fought hard to stay on terms with Surrey on day two at Taunton.
Azhar Ali and Steve Davies also weighed in with half-centuries as the hosts reached the close on 243 for five still 137 runs behind.
Rikki Clarke had earlier scored an unbeaten 59 to help Surrey achieve 380 in their first innings and then claimed the key wicket of Hildreth in the final session to give the defending champions the advantage at the halfway stage.
At Canterbury, Gary Ballance’s unbeaten half-century helped get Yorkshire back into their match with Kent.
The home side had taken an 86-run lead thanks to a second Championship hundred of the season from rookie wicketkeeper-batsman Ollie Robinson.
After dismissing Kent for 296, Yorkshire closed on 166 for three in their second innings to lead by 80 runs, with Ballance, reaching stumps on 57.
At Chelmsford, Simon Harmer saved Essex with the bat before causing panic with the ball in their clash with Nottinghamshire.
Harmer scored an invaluable 43 runs during an 81-run stand with Peter Siddle for the ninth wicket after Nottinghamshire, led by Luke Fletcher and Matt Carter, had ripped apart Essex’s middle order.
Having secured a 54-run first-innings lead, South African Harmer then found impeccable spin to claim figures of four for 32 as Nottinghamshire ended the day on 90 for six, with a slender lead of 36.
Kyle Abbott put Hampshire in total command against Warwickshire at Edgbaston.
After Hampshire were lifted to a solid 354 by Tom Alsop’s career-best 150, the home side advanced to 135 for three before South African paceman Abbott took three wickets for four runs in eight balls.
The follow-on figure of 204 was far from a formality for the hosts and they still have work to do to reach it, having closed day two on 184 for seven.
In Division Two, England batsman Keaton Jennings fell three runs short of a century before Lancashire’s strong start was checked by a fine new-ball spell from Northamptonshire.
The hosts had been 188 for two but slipped to 209 for six before Dane Vilas and Tom Bailey’s unbeaten 67-run stand steered their side to a lead of 46 runs with four wickets intact.
Jennings’ 97 and 67 from Rob Jones seemed to have given Lancashire control but Luke Wood hit back and finished the day with three for 44, while Ben Sanderson took two for 32.
At Lord’s, Ollie Rayner took four wickets on his first appearance of the season to keep Middlesex in control against Leicestershire.
The off-spinner removed Leicestershire’s half-centurions Harry Dearden and Colin Ackermann, who had threatened to take the game away from the home side with a fifth-wicket partnership of 110.
Leicestershire closed on 257 for nine, still trailing by 92 runs after the Seaxes posted a total of 349 in the morning.
Riki Wessels marked his home debut for Worcestershire with a century as his side established control against Durham.
The 33-year-old was eventually dismissed for 118 from 133 balls after hitting four sixes and 16 fours as Worcestershire closed on 321 for six and a lead of 48.
At Newport, Gloucestershire tightened their stranglehold on Glamorgan.
Ryan Higgins moved to three figures as Gloucestershire added another 103 runs to their overnight 360 for six, before reducing Glamorgan to 241 for eight – needing another 73 runs to avoid following on.