Richard Dawkins wrote a very simple computer program (Blind Snailmaker)
which he describes and illustrates in Chap 6 (Museum of All Shells)
in 'Climbing Mount Improbable'

There seem to be few shells that violate the straight vertical axis but
plenty that seem to violate the other axes.

If you plotted them, they would show a gradually increasing (and regular)
angle away from home, mainly due to the increase in tubular size of the
coils.

On the other hand, I have plenty of Vermetidae and Siliquariidae that
demonstrate no vertical axis discipline at all.

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