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The periostracum, as well as the coloration, is only rarely preserved in fossil shells. The apertural end of the gastropod shell is the anterior end, nearest to the head of the animal; the apex of the spire is often the posterior end or at least is the dorsal side. Most authors figure the shells with the apex of the spire uppermost.
Turritellidae, with the common name "tower shells" or "tower snails", is a taxonomic family of small- to medium-sized sea snails, marine gastropod molluscs in the Sorbeoconcha clade. They are filter feeders ; this method of feeding is somewhat unusual among gastropod mollusks, but is very common in bivalves .
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. In textbook illustrations of gastropod shells, the tradition (with a few exceptions) is to show most shells with the spire uppermost on the page.
Turritella is a genus of medium-sized sea snails with an operculum, marine gastropod mollusks in the family Turritellidae. [3] They have tightly coiled shells, whose overall shape is basically that of an elongated cone. The name Turritella comes from the Latin word turritus meaning "turreted" or "towered" and the diminutive suffix -ella. [4]
The shell of Semicassis pyrum has a large parietal callus, at the top in this image The shell of Cymatium pileare has a narrow parietal callus around the surface of the aperture nearest the columella, on the left of the shell opening as it is shown here. A parietal callus is a feature of the shell anatomy of some groups of snails, i.e. gastropods.
This shell has seven and a half whorls A fossil shell of the marine gastropod Turritella communis. 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 ...
Gastropods typically have a well-defined head with two or four sensory tentacles with eyes, and a ventral foot. The foremost division of the foot is called the propodium. Its function is to push away sediment as the snail crawls. The larval shell of a gastropod is called a protoconch.
This is the largest extant snail (shelled gastropod) species in the world, and arguably the largest (heaviest) gastropod in the world. Although the shell itself is quite well known to shell collectors because of its extraordinary size, little is known about the ecology and behavior of the species, [ 7 ] except for one study about its feeding ...