http://images14.fotki.com/v384/photos/9/901917/4085747/IMG_0235-vi.jpgAnd...then, with some progressive careful prying, and me jumping up and down as hard as I could on the 'downside' area of the 'ring'...some more prying, and...viola!!
http://images51.fotki.com/v628/photos/9/901917/4085747/IMG_0236-vi.jpgSo...I will see now about getting the rest of the Rim removed from the Tire, and to remove the Inner Tube, so I can patch it.
Tire had picked up a large Nail, puncturing the Inner Tube and occasioning a Flat.