Globe Sand Rails For Super Mario 64 In The World 'Shifting Sand Land' How Do You Find The 5th Star?

For Super Mario 64 in the world 'Shifting Sand Land' how do you find the 5th star? - globe sand rails

It's called the tox box switch star and you know the information about the track, but I can not understand. I know the world, as is the bright area where you must press the button and to run it before time runs out. But I can not understand that the button! I know it's likely star-shaped and yellow, but I can not find everywhere. Please give a detailed explanation, because I'm not the best with directions. Thank you and good luck!