Some 13 additional players have been called up to join the Scotland squad for preparations for Sunday’s RBS 6 Nations Championship match against Ireland at Murrayfield.The only absentee from the 23 on duty in the victory against Italy nine days ago is Euan Murray who is unavailable for round three for reasons of his Christian faith.The players called up are forwards:  Jon Welsh, Dougie Hall, Tom Ryder, John Barclay (all Glasgow Warriors), Alasdair Dickinson and Richie Vernon (Sale Sharks) and Grant Gilchrist (Edinburgh Rugby), backs:  Sean Kennedy, Alex Dunbar, Peter Horne, Peter  Murchie (all Glasgow Warriors), Tom Heathcote (Bath Rugby) and Nikki Walker (Worcester Warriors).The Scotland team to play Ireland is due to be announced on Wednesday.