Returning stalwarts strengthen Scotland
Scrumhalf Greig Laidlaw (ASM Clermont Auvergne), lock Richie Gray (Toulouse), centres Mark Bennett (Edinburgh) and Duncan Taylor (Saracens), and Worcester Warriors loose forward David Denton have all returned to the squad.
Laidlaw, Gray and Bennett haven't featured for the dark blues since last year's championship, while it was 2015 when returning prop Jon Welsh last saw international action and longer still for veteran hooker Scott Lawson (2014).
A sequence of untimely injuries has meant Denton has been absent from test duty since the 2016 tour to Japan, while Taylor and London Irish prop Gordon Reid missed the 2017 November Test campaign with a knee and head injury respectively.
Scarlets' John Barclay will continue to captain the side since taking on the mantle from Laidlaw in last year's championship, leading Scotland to victories in six of nine test matches.
There are also four uncapped players in a 40-man Scotland squad.
The potential debutants are Edinburgh trio Blair Kinghorn (fullback), scrumhalf Nathan Fowles and prop Murray McCallum, plus Glasgow Warriors prop D'arcy Rae.
"With the announcement of this 40-man squad, we are now entering the key stages of our preparation for this year's Six Nations Championship," said Scotland head coach Gregor Townsend.
"It's a bigger squad than we originally planned –which is largely down to the competition for places – with a number of players having performed well in the November Tests and a few others putting their hands up for selection in recent weeks.
"We welcome Blair Kinghorn into our group for the first time, who has been in excellent form with Edinburgh this season, and also three of our most experienced players in Richie Gray, Greig Laidlaw and Scott Lawson.
"We are looking forward to working with them and the rest of the squad to ensure that we build on the momentum the players generated in 2017."
In addition to the squad, three players have been invited to train with the group: Luke Crosbie (Edinburgh), Darcy Graham (Edinburgh) and Adam Hastings (Glasgow Warriors).
Backs: Mark Bennett, Alex Dunbar, Nick Grigg, Chris Harris, Stuart Hogg, Pete Horne, Ruaridh Jackson, Huw Jones, Lee Jones, Blair Kinghorn, Greig Laidlaw, Sean Maitland, Byron McGuigan, Ali Price, Henry Pyrgos, Finn Russell, Tommy Seymour, Duncan Taylor, Nathan Fowles,
Forwards: John Barclay (captain), Simon Berghan, Jamie Bhatti, Magnus Bradbury, David Denton, Cornell Du Preez, Grant Gilchrist, Jonny Gray, Richie Gray, Luke Hamilton, Rob Harley, Scott Lawson, Murray McCallum, Stuart McInally, Gordon Reid, D'arcy Rae, Ben Toolis, George Turner, Hamish Watson, Jon Welsh, Ryan Wilson.