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''Choristella tenera'' is a species of sea snail, a marine gastropod mollusk in the family Lepetellidae. ==Description== The shell grows to a size of 10 mm. The thin shell is fragile and has a smooth surface. It has a heliciform shape, with a low spire and a very large, ventricose body whorl. The shell contains four to five, very convex and evenly rounded whorls. The apical whorl is small, spiral, obliquely upturned and incurved, but not prominent. The suture is deeply impressed. The whorls are largely in contact and united well together, though the periostraca is continuous between them. The large aperture forms more than a half-circle. The outer sideof the aperture is well rounded, the columella margin nearly straight. The sharp lip is continuous all around, raised up and with the edge slightly everted in the umbilical region, so as to partially conceal the umbilicus, which is rather large and deep, nearly circular within. The thin operculum is horny, pale yellow, round-ovate, spiral, with two to three rapidly enlarging whorls, the nucleus excentric. The head of the animal is large, short, thick, rounded or truncate. It has two short, flat, obtuse, anterior tentacles, wide apart, but connected together by a ransverse fold. The posterior tentacles are short, thick, conical, smooth. There are no eyes visible. The proboscis is short, thick, and retractile. The ; crescent-shaped, black jaws are strong. The verge is situated just below the right posterior tentacle. It is small, papilliform, and swollen at base. Below this and farther back, there is a larger and thicker papilla with basal swelling. On each side, between the mantle and foot, at about mid length of the foot, there is a small mammiform papilla. There are also two small flat cirri, behind and beneath the operculum. The foot is broad, ovate, with two tentacle-like processes in front. The gill is large, consisting of numerous thin lamellae, attached to the inner surface of the mantle, over the left side of the neck, and extending obliquely across and over the neck to the right side.〔 (Verrill, A. E. 1882. Catalogue of marine Mollusca added to the fauna of the New England region, during the past ten years. Transactions of the Connecticut Academy of Arts and Sciences 5: 451-587, pls. 42-44, 57-58 ) 〕 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「Choristella tenera」の詳細全文を読む スポンサード リンク
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