Common Snapping Turtle (Chelydra serpentina) hatchling
9/9/11 David MD took pictures - It looks pretty young, and might still have its egg tooth (the white spot on its "nose"). (see description) After a bit more research, the egg teeth are supposed to fall off after a few hours, so the white spot in the pic might not be the egg tooth, or we've got a very recent hatchling here.