A spire is a descriptive term for part of the shell of a snail, a gastropod mollusc shell or gastropod shell. The spire consists of all of the whorls of a coiled gastropod shell except for the body whorl.
The word is a convenient aid in describing shells, it does not refer to an immutable part of shell anatomy. In textbook illustrations of gastropod shells, the tradition (with a few exceptions) is to show the the majority of shells with the spire uppermost on the page.
The spire, when not damaged, includes the protoconch (which is the larval shell), and most of the subsequent teleoconch whorls, which gradually increase in size as they are formed. Thus the spire in most gastropods has a point, which is known as the "apex". This is why the word "spire" is used, in analogy to a church spire.
Some gastropod shells have very high spires, some have low spires, and there are all possible grades between. In a few gastropod families the shells are not helical in their coiling, but instead are planispiral, flat-coiled. In these shells, the spire does not have a raised point, but instead is sunken.
Some different types of spire
Turbinoform or Turbinate: having a broadly conical spire and a convex base, as in Turbo, turban-shaped.
Turriform: with a many-whorled, slender spire, as in Turritella.
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