Coiling Direction of a Snail Shell

Looking at a snail shell, like this Ena montana, its coiling direction is easiest seen, when the aperture shows to the front and the apex points up.

If the aperture then is left of the shell's longitudinal axis, the shell is sinistral (left handed). If, like in Ena montana, the aperture is right of the shell axis, the shell is dextral (right handed).

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