This implementation of David Raup's parameter space for modeling shells is similar to the Demonstration contributed by Phil Ramsden. However, this model also allows for the manipulation of the shell thickness, a parameter potentially useful from a biological viewpoint. In certain species of snails, there is evidence that snail shell thickness correlates to the threat of predation from surrounding invasive species, such as crabs.
 G. Trussell and D. Smith, "Induced Defenses in Response to an Invading Crab Predator: An Explanation of Historical and Geographic Phenotypic Change," Proceedings of the National Academy of Sciences of the United States of America, 97(5), 2000 pp. 2123–2127. www.pnas.org/content/97/5/2123.full.