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The corded purg, scientific name ''Pyrgulopsis nevadensis'', is an extinct species of freshwater snail with a gill and an operculum, an aquatic gastropod mollusk in the family Hydrobiidae. ''Pyrgulopsis nevadensis'' is the type species of the genus ''Pyrgulopsis''.〔Call R. E. & Pilsbry H. A. 1886. ''On Pyrgulopsis, a new genus of rissoid mollusk, with description of two new forms''. (Proceeding Davenport Academy of Natural Sciences, volume V. ), page (9 )-14. (Plate II. ), figures 1-10.〕 == Shell description == The shell is small, somewhat elongated, variable, turreted and imperforate. The shell has 4½-5½ whorls, that are strongly unicarinate on periphery, otherwise smooth. The epidermis is shining, light straw in color or whitish. The suture is white. The suture is deeply and regularly impressed, made conspicuous by the approximating carina.〔 There existed also smooth variation. ((plate II, figure 6-8. )) The aperture is very oblique, roundly ovate, with an angle on outer edge corresponding to the excavated carina, posteriorly sharply angled, well rounded before. The peritreme is continuous, almost rimate, closely appressed to parietal wall.〔 The operculum is light corneous, spiral and closely fitting the aperture.〔 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「Corded purg」の詳細全文を読む スポンサード リンク
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