"Dome Fossil Rock Smash - Postgame - X Only"
"Helix Fossil Rock Smash - Postgame - Y Only"
www serebii net/pokearth/kalos/glitteringcave.shtml
In Glittering cave is incorrect, I just found both a Dome and Helix Fossil from using Rock Smash in that cave on Pokemon Y
www i.imgur com/Swa47D9.jpg
(Unable to post URLS)
Edit: Found 1 more of each and took a picture of me obtaining it for further proof