Calcareous
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Calcareous is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.
Calcareous sandstone in Seven Sisters Country Park, England
Calcareous mine in Perm Krai, Russia
Mollusca
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Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks. 86,600 extant species of molluscs are recognized, making it the second-largest animal phylum
Cornu aspersum (formerly Helix aspersa)—a common land snail
Shell of Marisa cornuarietis, a freshwater snail
Fossilized ammonite displayed at the National Museum of the Philippines
Diversity and variability of shells of molluscs on display