I month or so ago I was talking with a neighbor about my garter snakes. He suddenly said that he had a two headed garter snake many years ago(30 he figured). I thought, rrrrright. He then said he still had the skeleton somewhere at his parent's house. I told him I would love to see that.
Well, he came to the door a few minutes ago and sure enough. He said the snake lived about a week and that both heads were alive and flicking their tongues. I'm guessing T.radix.