Scarlets players' player of the year, full-back, Liam Williams, his regional team-mate, prop, Rhodri Jones, Ospreys centre Ashley Beck and Blues wing Harry Robinson (promoted from the Wales U20 squad) are the four uncapped players named, although all four have figured in previous national squads - as recently as the 2012 Grand Slam winning RBS 6 Nations campaign in the case of Williams and Robinson.
Back in contention - called up from outside of this season's all conquering Six Nations squad - are Ospreys backs Dan Biggar (fly-half), and Andrew Bishop (centre), Scarlets flanker Josh Turnbull and Dragons wings Aled Brew and Will Harries, alongside Blues flanker Martyn Williams who is set to win his 100th cap against the Baa-Baas.
"The Ospreys will have our full backing in their bid for silverware in a fortnight's time so we will not be asking them to join us until a week after everyone else," said Howley.
"They are playing very well at the moment, a win in the final would be a great starting point for our own campaign this summer and the call ups for both Dan (Biggar) and Andrew (Bishop), in particular, reflect the good form the Ospreys are in.
"Elsewhere we have been pretty consistent with selection, it's now down to these players to pick up where we left off in the Six Nations and prove to us that they should be on that plane to Australia.
"We hope to get the summer off to a winning start against the Baa-Baas and everyone who figures in that game will be playing for a place on the tour."
Whilst Wales' Ospreys contingent will not be in camp until Monday 28th May, Howley is confident he will have a full strength squad to choose from by the time he comes to select his side to face the Baa-Baas, with his overseas contingent available and fitness worries over certain players abating.
"Both Mike (Phillips) and James (Hook) will be with us from the start, Sam (Warburton) is still on track and we are optimistic that both Jonathan Davies and Scott Williams will have reached full fitness and be able to play their part in the tour," added Howley
"We have a tough series ahead of us with five matches in four weeks and two games in two separate Hemispheres in the space of seven days, but we are fully focussed on the prize of that elusive Southern Hemisphere scalp."
Clermont Auvergne fullback Lee Byrne is not selected as he is still likely to be involved in domestic competition in France right up to the date the tour party leaves (the Top 14 players Final, for which his club are still in contention, will be held on 9th June), however, he will remain on standby for the tour.
Unavailable due to injury are Blues centre Jamie Roberts and Ospreys hooker Huw Bennett.
Wales' fourth capped meeting with the Barbarians (the Baa-Baas currently lead the series 2-1) will be sponsored by Under Armour under the tagline - 'Wales v Barbarians, powered by Under Armour' - it was announced today.
Also confirmed this morning is the mid-week fixture on tour between Wales and the ACT Brumbies, who are leading the Australian Conference in the southern hemisphere provincial championship. Wales play three Tests against Australia in Brisbane on June 9, Melbourne on June 16 and Sydney on June 23 and will take on the Super 15 provincial team at Canberra Stadium on June 12 to complete their largest ever one-nation tour.
Extended Training Squad For Baa Baas & Australia Tour 2012
Forwards: Ryan Bevington, Luke Charteris, Brad Davies, Ian Evans, Toby Faletau, Rhys Gill, Richard Hibbard, Paul James, Gethin Jenkins, Adam Jones, Alun Wyn Jones, Rhodri Jones, Ryan Jones, Dan Lydiate, Ken Owens, Matthew Rees, Aaron Shingler, Justin Tipuric, Josh Turnbull, Sam Warburton, Martyn Williams.
Backs: Ashley Beck, Dan Biggar, Andrew Bishop, Aled Brew, Alex Cuthbert, Jonathan Davies, Leigh Halfpenny, Will Harries, James Hook, George North, Mike Phillips, Rhys Priestland, Harry Robinson, Rhys Webb, Lloyd Williams, Scott Williams, Liam Williams