A figure formed by taking a series of steps of length 1, 2, ..., , with an angle turn after each step. The symbol for a spirolateral is , where the s indicate that turns are in the direction for these steps.
See also Maurer Rose, Spirograph
References
Gardner, M. ``Worm Paths.'' Ch. 17 in Knotted Doughnuts and Other Mathematical Entertainments.
New York: W. H. Freeman, 1986.
Odds, F. C. ``Spirolaterals.'' Math. Teacher 66, 121-124, 1973.