I recently picked up a Nishiki Century road bike (large frame). The rear derailleur was not mounted when I got it, it was just hanging on the chain. I took the chain off, and cleaned the derailleur. The problem is, I'm not sure how it's supposed to mount on the frame. There doesn't seem to be any holes to bolt it on. I'm including a picture of both the mounting point and the derailleur.
I'm stumped. Any ideas?