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A spire is a part of the coiled shell of molluscs. The spire consists of all of the whorls except for the body whorl. Each spire whorl represents a rotation of 360°. A spire is part of the shell of a snail, a gastropod mollusc, a gastropod shell, and also the whorls of the shell in ammonites, which are fossil shelled cephalopods.
This shell has nine whorls. A whorl is a single, complete 360° revolution or turn in the spiral or whorled growth of a mollusc shell. A spiral configuration of the shell is found in numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the ammonites.
The largest height of any shell is found in the marine snail species Syrinx aruanus, which can be up to 91 cm. [14] 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.
The shell is coiled, aragonitic, [22] nacreous and pressure-resistant, imploding at a depth of about 800 m (2,600 ft). The nautilus shell is composed of two layers: a matte white outer layer with dark orange stripes, [23] and a striking white iridescent inner layer. The innermost portion of the shell is a pearlescent blue-gray.
Siphonal canal – semi-tubular extension of the aperture of the shell through which the siphon is extended when the animal is active; Spatulate – In the form of a spatula, a flat-bladed instrument used by druggists in pulverizing drugs. [1] Spherical – Shaped like a sphere. [1] Spiral – Wound about a central cavity, as the whorls of ...
In gastropods, the body whorl, or last whorl, [1] is the most recently formed and largest whorl (or revolution) of a spiral or helical shell, terminating in the aperture.It is called the "body whorl" because most of the body of the soft parts of the animal fits into this whorl.
The more or less turret-shaped shell consists of tightly-wound (sometimes loosely coiled), convex whorls, which create a high, conical spiral. Fine or microscopic spiral sculpture (also called "striae") is present in many species. The shells sometimes feature an umbilicus.
The inner layers of the shell are composed of a network of calcium carbonate, conchin, and different mineral salts. The mantle produces the shell through addition around a central axis called the columella, causing a spiraling pattern. [10] The spiraling patterns on a snail’s shell are known as coils or whorls. Whorl size generally increases ...