The word snail is given to gastropods that have a coiled shell large enough for the animal can retract inside it.
Spirorbis is a genus of very small (2-5mm) polychaete worms, usually with a white coiled shell.
These snails all have a coiled shell present in their larval stage.
According to S. J. Gould's interpretation of Dollo's law, it would not be possible to regain a coiled shell after the coiling has been lost.
Tylonautilus has a coiled shell with a subquadrate whorl section, evolutely coiled with all whorls showing.
The body whorl is part of the morphology of the shell in those gastropod mollusks that possess a coiled shell.
The word is also applied to the depressed central area on the planispiral coiled shells of Nautilus species and fossil ammonites.
However, like all the snails in the subfamily Planobinae, this snail carries its coiled shell upside down, and thus the shell appears to be dextral in coiling.
This coiled shell usually opens on the right-hand side (as viewed with the shell apex pointing upward).
It was just as the gnome had remembered it: a golden coiled shell, set upright, from the mouth of which several interwoven wooden tentacles projected forward, forming a pointed bow.