Wes Agar's five-wicket haul headlined a day out for a trio of Aussie pacemen across the two country divisions, while leg-spinner Swepson also bowled on debut
Aussie quicks in thick of County Championship action
Five wickets for Wes Agar has capped a good day for Australian bowlers in the county championship, with Sean Abbott and Nathan McAndrew claiming four-wicket hauls in their respective matches.
Agar's 5-63 helped Kent bundle out Northamptonshire for 237 on the opening day of their Division One clash at Northants' home ground.
Agar struck in his second over to give Kent the perfect start after Northants won the toss and opted to bat first, then removed Western Australia batter Sam Whiteman after he made 40, breaking a 62-run stand with Rob Keogh.
Keogh then became Agar's third victim, falling for 97, as the South Australia quick changed the game, picking up two more quick wickets in his next over.
Kent had rattled along to 1-110 in reply by stumps after an unbeaten 58 from 22-year-old Zimbabwe-born opener Tawanda Muyeye.
It was a bowlers' day at The Oval as Abbott collected 4-71 for Surrey after they opted to bowl first in their Division One clash with Lancashire in south London.
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Coming on second change, Abbott struck with his first delivery to remove Lancs' No.3 Josh Bohannon leg before for 10, before claiming the scalp of skipper Keaton Jennings for 25, also lbw.
His second spell after lunch saw him strike again to remove Dane Vilas for 39 and he returned in the third session to end Phil Salt's innings on 56, caught at slip.
Abbott struggled with his front foot, however, conceding 12 no-balls.
Four wickets for Abbott's teammate Jordan Clark saw Lancashire bowled out for 274, but Surrey's top order limped to 4-70 at the close.
At Cardiff's Sophia Gardens in Division Two, McAndrew was the pick of the bowlers with 4-58 from 16.5 overs as his Sussex side bowled out Glamorgan for 242 in a match using Kookaburra balls as part of an experiment to help English players adapt to Australian conditions.
McAndrew struck in his sixth over when he had Sam Northeast caught for 17. After being hit for back-to-back fours by Kiran Carlson to start his second spell, the Redbacks allrounder had his revenge next over when Carlson was caught out for 27.
McAndrew's fourth spell saw him wrap up the Glamorgan tail with two quick wickets, including bowling Queensland leg-spinner Mitchell Swepson.
Swepson, who has joined the county for a spell following fellow Queenslander Michael Neser's call-up to the Australian Test squad, then bowled seven tight overs as first change without a wicket as Sussex reached stumps at 1-65.
Australians in the County Championship
Durham: Matthew Kuhnemann
Essex: Daniel Sams (T20s only)
Glamorgan: Marnus Labuschagne, Michael Neser, Peter Hatzoglou (T20s only), Mitchell Swepson
Gloucestershire: Marcus Harris
Hampshire: Nathan Ellis, Ben McDermott (both T20s only)
Kent: Wes Agar, Kane Richardson (T20s only)
Leicestershire: Peter Handscomb (April and May)
Northamptonshire: Chris Tremain (April 6-23), Jordan Buckinhgam (May 1-21), Sam Whiteman (until August), Chris Lynn (T20s), Andrew Tye (T20s)
Somerset: Peter Siddle (until July), Cameron Bancroft (until May 7)
Surrey: Sean Abbott (until July), Dan Worrall (UK passport)
Sussex: Nathan McAndrew (until July), Steve Smith (May 4-21)
Warwickshire: Glenn Maxwell (T20s only)
Yorkshire: Mickey Edwards (UK passport)