Injured Snapping Turtle
If you clook closely you will see that he only has one eye. And, I know that snappers do not have teeth, but it surely looks like small teeth in these photos.
Unfortunately, the reason for his walking in circles became clear - this snapper had been run over by a car - the rear right shell was damaged and bloody - the rear right leg clearly damaged. I finally managed to move him (using the stick) to the side of the road. I doubt that he made it. You can find a great snapping turtle at http://www.tortoisetrust.org/articles/snappers.htm.