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''Anostoma'', common name the up-mouth snails, is a genus of tropical air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Odontostomidae.〔Breure A. S. H. & Ablett J. D. (2012) "Annotated type catalogue of the Bothriembryontidae and Odontostomidae (Mollusca, Gastropoda, Orthalicoidea) in the Natural History Museum, London". ''ZooKeys'' 182: 1-70. .〕 Snails in this genus are found in Brazil. Adult snails in this genus have an extremely unusual shell morphology: the aperture of the adult shell faces directly "upwards", in other words, in the same direction as the spire.〔 This seemingly impossible arrangement is made possible because the adult shell is carried upside down. In 1901, the American malacologist Henry Augustus Pilsbry〔 commented that the adult shell of ''Anostoma'' is "so bizarre that in the total absence of information upon its life history, no useful theory can be formulated to account for its peculiarities." A very similar shell is found in the genus ''Ringicella'' Gray, 1847, which was previously considered to be merely a subgenus within ''Anostoma'', but it is now considered to be a genus in its own right. == How the shell is carried== This is one of the most peculiar genera of land snails. The prominent feature of an upturned aperture (causing the adult snail to carry the shell spire down) is reflected in its scientific name ''Anostoma'': ''ano'', means up, or backwards, and ''stoma'' means mouth, from the Greek.〔 In this genus, the adult snails carry the shell completely upside down, with the umbilicus uppermost, and the spire facing downwards. To make this extraordinary feat possible, the mature aperture of the shell is aligned in the same plane as the rather low spire of the shell. It appears that in juveniles, the shell is carried with the widest diameter vertically aligned, in other words, with the keel of the shell pointing up.〔Heath H. 1914. ''The anatomy of two Brazilian land-shells, Anostoma depressum and Tomigerus clausus''. (Proceedings of the Academy of Natural Sciences of Philadelphia, 65 ): (688 )-692, (plate 31 ) ().〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Anostoma」の詳細全文を読む スポンサード リンク
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