[Lewis Thomson (OP)]

Christopher wants to learn the answer to this question.

"Does the direction of spiralled sea shell be dictated by the shells hemispheric location? I wonder this because I think most sea shells I have seen seem to spiral in the same direction. Also, as I am aware that water, depending whether in the Northern or Southern hemisphere, goes in different directions down a drain, so maybe it had the same effect on sea shells."

What do you think? Discuss your findings in the comments below...

[chiralSPO]

I don't think there is proof that there is NOT ANY influence of the hemisphere, but if there is any, it is VERY, VERY slight.

From a physics standpoint, the Coriolus effect comes from the relationship of angular momentum and torque in correlated spinning systems. It is really only significant for very large spinning systems (like hurricanes or other weather systems), and has essentially no influence on which direction is favored for water going down a drain (it is a non-zero influence, but almost certainly less significant than slight imperfections in the drain or basin itself, or as is the case with toilets, which direction the water is being pushed). It would be an even more tenuous connection linking something essentially static (shells with right-handed or left-handed twists don't have different angular momenta unless they are spinning differently—I don't think growth would be a factor)

From an biological (and observational) standpoint, the twists don't appear to depend on where the shell matured. It appears largely species-dependent (genetically determined).  The following article discusses some biochemical (gene editing) studies that demonstrate that, at least for some snails, we can identify which gene(s) is (are) involved in determining how the chirality gets defined.
https://www.pbs.org/newshour/science/how-a-snails-shell-gets-its-twist