Sinistral: extending to or at the left from the median line.
If we were very fortunate, we might find a sinistral, or “left-handed” specimen.
Sinistral: Having the aperture of the shell at the left; opposite of dextral.
This is carried outward in a sinistral spiral to the noded shoulder.
Gasteropod shells may be sinistral or dextral, according as the whorls turn to the left ...