In American folklore, the Hoop Snake is a snake that forms itself into a hoop and travels along with its tail in its mouth, just like a wheel. Although belief in it dates from at least the 18th Century, the scientific community has always been skeptical of the existence of this animal. The magazine Natural History called it a myth in 1925. Leon Hale of the Houston Chronicle, however, has received many reports of this animal, though none have been recent.
Similar snakes have occurred in the folklore of Sweden. They were said to live in Lakes Regneven and Alsjon and travel between the two in the form of a hoop. They were regarded as very dangerous and would attack children. However, there have been no reports of them for 200 years.
Here in Ireland, where there are no snakes, the same behaviour has been ascribed in folklore to eels.
I suspect it is possible that we have behind this legendary creature, not a separate species, but a practice in which various kinds of snake occasionally indulge. However, this is just speculation on my part.