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The Trochidae, common name top snails, are a taxonomic family of very small to large sea snails, marine gastropod molluscs in the clade Vetigastropoda (according to the taxonomy of the Gastropoda by Bouchet & Rocroi from 2005). This family is commonly known as the "top snails", because in many species the shell is shaped like a toy top. ==Anatomy== The animal is similar in general form to the Turbinidae. The top snails are characterized by some primitive traits: a heart with two atria. They have retained only one kidney and the second osphradium has been lost in the course of evolution. The mantle cavity contains a single gill. Along the side of the foot are three or more pairs of sensory epipodial tentacles. The head has a short, broad rostrum. The intertentacular lobes are simple or digitated, separate or united across the front, sometimes obsolete. The jaws are developed or absent. 〔 The radula is rhipidoglossate. The rhachidian teeth are always present and well-developed. The lateral teeth generally number 5 on each side, sometimes more numerous. The marginal teeth are narrow and very numerous. 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「Trochidae」の詳細全文を読む スポンサード リンク
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