I thought I as going to manage to complete this one without the aid of the forum for once, but I got stuck on 15,25, so thanks all for the tips.
While writing, I note that the errors in the Crucible one three weeks ago have been corrected, both online and in the Corrections column in the printed paper, but only after the closing date for entry. I wonder, therefore, how they chose the winners: did they accept the correct spelling - mesozoic - which did not parse, or the incorrect spelling - mezozoic - which did - or either?