The Cambridge natural history . last whorl becomesdisconnected from the others, as in Rhiostoma (see Fig. 180, ), Teinostovi((, and in the fossil Ophidioceras and , again, not more than one or two whorls at the apexare spirally coiled, and the rest of the shell is simply produced orcoiled in an exceedingly irregular manner, Cydosurus, Lituites,Oryfioceras, Siliquaria (Fig. 153), Vermetvs. In Coecum (, p. 260) the spiral part is entirely lost, and the shell becomessimply a cylinder. In a few cases the last whorl is coiled irregu-larly backwards, and i

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The Cambridge natural history . last whorl becomesdisconnected from the others, as in Rhiostoma (see Fig. 180, ), Teinostovi((, and in the fossil Ophidioceras and , again, not more than one or two whorls at the apexare spirally coiled, and the rest of the shell is simply produced orcoiled in an exceedingly irregular manner, Cydosurus, Lituites,Oryfioceras, Siliquaria (Fig. 153), Vermetvs. In Coecum (, p. 260) the spiral part is entirely lost, and the shell becomessimply a cylinder. In a few cases the last whorl is coiled irregu-larly backwards, and is brought up to the apex, so that the animalill crawling must carrv tlie shell with the spire downwards., as in 248 FORMS OF THE SPIRAL Anostoma (Fig. 154), Opisthostoma (Fig. 208, p. 309), Strojiho-stonia, and Hy2)selostoma (Fig. 202 A, p. 302). Some genera of the Capulidae, in wliicli the shell is of ahroadly conical form or with scarcely any spire, develop aninternal plate or process which serves the ])urpose of keeping the.

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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895