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Capulus ungaricus, common name the bonnet shell, is a species of medium-sized sea snail, a marine gastropod mollusk in the family Capulidae, the cap snails. [ 1 ] Taxonomy
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.
The shell is an exoskeleton, which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium storage. Some gastropods appear shell-less but may have a remnant within the mantle, or in some cases the shell is reduced such that the body cannot be retracted within it .
The shell of Stenotrema florida, a land snail or terrestrial gastropod.The periostracum of this species has minute hairs, giving the snail a velvety feel A yellowish tan periostracum is visible on the lower two thirds of this juvenile (8 cm) valve of the marine bivalve Spisula solidissima The dark periostracum is flaking off of this dried-out valve of the "ocean quahog", marine bivalve Arctica ...
In other words, in gastropods whose shells have varices, the shells are characterised by episodic growth - the shell grows in spurts, and during the resting phase the varix forms. In many gastropod whose shells have varices, for example the Cassinae , the varix is essentially merely a thickening and swelling of the shell at that point.
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.
The side of the shell which is in fact the spire (a sunken spire) faces down in the living animal, contrary to what is the case in almost all other shelled gastropods. Because the shell is carried "upside down" like this, the aperture of the shell is angled to face downwards also, so the aperture faces a little towards the spire, not away from ...
shell of Rhodacmea filosa 31 May 2011 - the Wicker ancylid Rhodacmea filosa, (shell pictured) listed as extinct by the IUCN Red List, has been rediscovered. New gastropod taxa described in 2011; 18 April 2011 - Research on the mating of Chelidonura sandrana contradicts the traditional theory about mating in simultaneous hermaphrodites.