Wales head coach Warren Gatland has named four uncapped players in his squad for the Guinness Six Nations Championship.Ospreys centre Keiran Williams, Cardiff centre Mason Grady, Ospreys lock Rhys Davies and Cardiff second-row forward Teddy Williams have all been selected.The quartet are the only international rookies among a 37-man group, with Gatland's second spell as Wales boss beginning at home to Ireland on 4 February.Scarlets hooker Ken Owens has been appointed captain, being preferred to other candidates such as Justin Tipuric, Dan Biggar and Alun Wyn Jones.Wales squad:Forwards: Rhys Carre (Cardiff), Wyn Jones (Scarlets), Gareth Thomas (Ospreys), Dewi Lake (Ospreys), Ken Owens (Scarlets, capt), Bradley Roberts (Dragon), Leon Brown (Dragons), Tomas Francis (Ospreys), Dillon Lewis (Cardiff), Adam Beard (Ospreys), Rhys Davies (Ospreys), Dafydd Jenkins (Exeter Chiefs), Alun Wyn Jones (Ospreys), Teddy Williams (Cardiff), Taulupe Faletau (Cardiff), Jac Morgan (Ospreys), Tommy Reffell (Leicester Tigers), Justin Tipuric (Ospreys), Christ Tshiunza (Exeter Chiefs), Aaron Wainwright (Dragons).Backs: Kieran Hardy (Scarlets), Rhys Webb (Ospreys), Tomos Williams (Cardiff), Dan Biggar (Toulon), Rhys Patchell (Scarlets), Owen Williams (Ospreys), Mason Grady (Cardiff), Joe Hawkins (Ospreys), George North (Ospreys), Nick Tompkins (Saracens), Keiran Williams (Ospreys), Josh Adams (Cardiff), Alex Cuthbert (Ospreys), Rio Dyer (Dragons), Leigh Halfpenny (Scarlets), Louis Rees-Zammit (Gloucester), Liam Williams (Cardiff).