More than 35 000 species The members of this large group have both tentacles and eyes. The visceral mass is horizontally twisted through 180 degrees, so that the body is not symmetrical. There is a single shell, but in some forms the shell is very small or absent altogether. A typical shell is a conical spire composed of tubular whorls. All the land molluscs belong to this group, as well as many aquatic gastropods. |
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