Shell formation

[hawkeye]

I've always been facinated about how and why many shells form a spiral shape, and the relationship of this shape to similar shapes in other parts of nature, i.e. galaxies, flowers, hurricanes, tornadoes, black holes, etc. Most of you know about the Fibinocci sequence and the "golden triangle" which mathematically explains the basis for the spiral effect. As part of my research into this topic, which I plan to present to a stamp club, by way of stamps depicting shells, I would like to know where I would find references to shell formation.  <img src="images/smiley/confused.gif" alt="" border="0" />