CHAPTER VII
Periwinkles
Conchs and Other Snails
Class Gastropoda
Superfamily Pleurotomariacea
Family Scissurellidae
Genus Scissurella Orbigny 1823
Subgenus Schizotrochus Monterosato 1884
Massachusetts to eastern Florida and the West Indies. Europe.
3.5 mm. (1⁄8 inch) in width and 3.0 mm. in length. 4 to 5 whorls. Fragile, frosty-white in color and sculptured by very delicate reticulations. Umbilicus small, round and very deep. Periphery of whorls angulate and with two thin, sharp spiral lamellae. Between these there is an open slit running from the edge of the thin apertural lip back about 1⁄5 of a whorl. Uncommon from 60 to 500 fathoms.
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Figure 29. Florida Slit-shell, Scissurella proxima Dall, 1⁄16 inch (Massachusetts to Florida, 20 to 430 fathoms).
The Florida Slit-shell, S. proxima Dall (fig. 29), from South Carolina to the Lower Florida Keys, differs in being half as large, with a more rounded periphery, and a higher spire, so that the length is about equal to the width of the shell, and in having a weaker pair of peripheral lamellae. Uncommon from 20 to 430 fathoms.
Family Pleurotomariidae
Genus Perotrochus P. Fischer 1885
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