"The Trochidae, common name top-snails or top-shells, are a taxonomic family of very small to large sea snails, marine gastropod molluscs in the clade Vetigastropoda (according ...
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to the taxonomy of the Gastropoda by Bouchet & Rocroi from 2005).
This family is commonly known as the "top-snails" because in many species the shell resembles a toy spinning top." - (en.wikipedia.org 24.07.2021)