After you have passed the checkway point flag, if you go forward you should get to a
strange ball-like thing which you stand on one side of to roll. When you get to the land
after that there should be a dry-bones and a dragon-thing. Then there is mesh-cylindar
thing which again, you stnd on one side to roll. Halfway through the lava river on the
mesh cylindar there should be a mesh platform. Stand on the middle of the plaform and wait
for it to sink a bit. The star coin is in the middle of the platform but underneath. By
the way, make sure you watch out for the lava geysor under the mesh platform! Sorry for my
answer being so long but i didn't want you to get it wrong. Hope i helped!!! ^. ^