You can model one grec motif, then use Transform/Array /Curve
Curve is of course an oval!
Before that your motif must be deform on the top if you want a perfect assembling :)
Hope this help !
I took here Epsilon :)
Yeah Pilou, I was trying to imitate the ornament in the picture that doesn't seem deformed (curved edges) but is perfectly possible to draw a single piece using centerlines as you show in your picture. :)