Map Turtles -- for real

On my FaceBook page, I'd let my friends know that I'd cleaned two map turtles this week from our oil spill back in July.

One friend commented back, "What in the world is a map turtle?"
Another added, "I'm glad someone else asked that question."

I wrote back (something like, without looking it up):
"A map turtle is a creature which, if you're lost and rub its underbelly, then put it down, you can follow it wherever you want to go."

(Actually, if you just do a search for it, lots of sites pop up about map turtles.)