Dimensions
The most frequently used measurements of a gastropod shell are: the height of the shell, the width of the shell, the height of the aperture and the width of the aperture. The number of whorls is also often used.
In this context, the height (or the length) of a shell is its maximum measurement along the central axis. The width (or breadth, or diameter) is the maximum measurement of the shell at right angles to the central axis. Both terms are only related to the description of the shell and not to the orientation of the shell on the living animal.
The largest height of any shell is found in the marine snail species Syrinx aruanus, which can be up to 91 cm.
The central axis is an imaginary axis along the length of a shell, around which, in a coiled shell, the whorls spiral. The central axis passes through the columella, the central pillar of the shell.
Read more about this topic: Gastropod Shell
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