Planispiral
Appearance
![](http://upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Anisus_septegyrus1pl.jpg/220px-Anisus_septegyrus1pl.jpg)
Planispiral is a condition in which a tubicolous shell is coiled in a single horizontal plane and the diameter increases away from the axis of coiling. This term is usually used for describing gastropod shells. Many cephalopods and tubeworms can also have a planispiral shell (Allaby and Allaby, 1999).
References
- Allaby, A.; Allaby, M. (1999). "Planispiral". A Dictionary of Earth Sciences. Retrieved 2014-01-13.
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