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The mollusc (or mollusk [a]) shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea; many live on the land and in freshwater.
The iridescent nacre inside a nautilus shell Nacreous shell worked into a decorative object. Nacre (/ ˈ n eɪ k ər / NAY-kər, also / ˈ n æ k r ə / NAK-rə), [1] also known as mother-of-pearl, is an organic–inorganic composite material produced by some molluscs as an inner shell layer. It is also the material of which pearls are composed.
Umbilicus: in shells where the whorls move apart as they grow, on the underside of the shell there is a deep depression reaching up towards the spire; this is the umbilicus; Varix: on some mollusk shells, spaced raised and thickened vertical ribs mark the end of a period of rapid growth; these are varices
Abalone shells and associated materials, like their claw-like pearls and nacre, have been used as jewelry and for buttons, buckles, and inlay. [ 15 ] [ 16 ] [ 17 ] These shells have been found in archaeological sites around the world, ranging from 100,000-year-old deposits at Blombos Cave in South Africa to historic Chinese abalone middens on ...
Instead, a segmented shell gland forms on one side of the larva, and a foot forms on the opposite side. When the larva is ready to become an adult, the body elongates, and the shell gland secretes the plates of the shell. Unlike the fully grown adult, the larva has a pair of simple eyes, although these may remain for some time in the immature ...
The apex of the shell is fragile and it is corroded in adults. [2] This is a very large peltospirid compared to the majority of other species, which are usually below 15 millimetres (3 ⁄ 5 in) in shell length. [2] The width of the shell is 9.80–40.02 mm (0.39–1.58 in); [2] the maximum width of the shell reaches 45.5 millimetres (1.79 in). [2]
Cornu aspersum (formerly Helix aspersa)—a common land snail Shell of Marisa cornuarietis, a freshwater snail. Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks [a] (/ ˈ m ɒ l ə s k s /). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal ...
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