Left-handed spiral
From WikiEducator
Orient your snail with the pointed spire facing up. With your thumb pointing up, imagine wearing the snail shell like a glove. If your left hand would best fit in the opening of the shell, then it is a left-handed snail; if your right hand would best fit in the shell, then you have a right-handed snail.
File:Physa fontinalis.jpg
Figure 1. Examples of left-handed snail shells.
Right-handed spiral
File:Lymnaea stagnalis (Linné, 1758) (4901291115).jpg
Figure 2: Examples of right-handed snail shells.
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