Axle C-clips have a flat surface and a more rounded surface.

I assume that the flat srface will face the spider gear.
Is this correct or the other way?

 

The C-clips are stamped-out in the manufacturing process (like flat washers) and that is what you're seeing (somewhat rounded on one side and flat on the other). There really isn't any correct, or wrong way to insert them. However, you can look at the old wear marks (round ring for the axel tip, flat for the spider gear) and put them back in the same way.

WD

 

Unfortunately I have had the c-clips out many times so I cant verfy the original orientation. I just bought new ones and want to get it right if there is a right.