#shell

• Acanthoceras — A genus of extinct fossil cephalopod mollusks (ammonites) within the Acanthoceratidae family, characteristic of the Late Cretaceous epoch. These marine organisms were distinguished by their massive, planospiral coiled shells heavily ornamented with prominent ribs and rows of sharp tubercles or spine-like outgrowths along the outer whorls, serving as critical index fossils for dating geological strata of that period.
• Protective shell — A rigid anatomical structure resembling a shield, shell, test, or protective skeletal frame, composed of calcareous, chitinous, or siliceous matter, which partially or fully encloses the body of certain invertebrates (such as some crustaceans, mollusks, or protozoans). It serves an essential function as a predator barrier, structural support for soft tissues, and defense against dehydration.
• Aegoceras — An extinct genus of ammonoid cephalopods within the order Ammonitida and family Liparoceratidae, which thrived during the Early Jurassic epoch (predominantly in the epicontinental seas covering modern Western Europe). The shells of these ammonites are evolute, characterized by widely open whorls, rounded whorl sections, and prominent, well-spaced transverse ribs, holding significant stratigraphical value as index fossils for mapping geological strata.
• Shell game — An illegal and fraudulent game of chance, usually practiced in crowded public places (fairs, markets, stations), consisting of spectators guessing the hidden object (a ball, a coin) under one of three cups, thimbles, or playing cards manipulated quickly and with manual skill by a swindler. In a figurative sense, the term describes an action based on deception, manipulation, hidden tricks, or a duplicitous strategy by which the truth is concealed.
• Alpinia speciosa — The scientific Latin designation (a synonym frequently used in literature for Alpinia zerumbet) denoting shell ginger or ginger lily, a large-sized perennial herbaceous plant species in the Zingiberaceae family, native to East Asia. This spectacular ornamental plant stands out structurally due to its long, drooping inflorescences consisting of large flowers resembling pinkish-white porcelain shells and an intensely colored labellum in bright shades of yellow and red, widely cultivated in tropical regions and greenhouses.
• Ancyloceras — A genus of fossil ammonites from the Early Cretaceous period, characterized by a partially uncoiled or unusually bent shell, often with an initial spiraled portion followed by a straight shaft and a final hook-like bend. It represents a reference organism in biostratigraphy for the precise dating of marine geological strata.
• Arcella — A genus of testate amoebae (protozoa) characterized by a protective organic shell or test, often dome, disc, or hat-shaped, made of chitinous material with a single central pseudopod opening. In a structural sense, arcella represents a microscopic unicellular organism that inhabits freshwater habitats, peat bogs, and damp moss, serving as an excellent bioindicator for environmental quality and ecosystem pollution levels.
• Ash — Neologism borrowed from English used in the computing and digital environment; a command language or shell in Unix operating systems; ash (on a structural level, in literary translations or role-playing games where it defines a magical element, a state of degradation, or a famous character). In pop culture, it also represents the reference name of the main protagonist from the Pokémon animated series (Ash Ketchum).
• Astaciform — Having the shape, appearance, or anatomical structure resembling that of a crayfish (of the genus Astacus); a morphological adjective used in biology to describe the exterior appearance of certain fossil or contemporary crustaceans presenting a robust cephalothorax, segmented abdomen, and prominent claws.
• Aulacoceras — An extinct genus of dibranchiate cephalopods from the order Belemnoidea, characteristic of the Triassic period. This ancient marine organism was notable for an elongated, conical, calcareous internal shell marked on its outer surface by prominent longitudinal grooves.