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History of British animals - University of Guam Marine Laboratory

History of British animals - University of Guam Marine Laboratory

History of British animals - University of Guam Marine Laboratory

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MOLLUSCA. HOLOSTOMATA. 297HOLOSTOMATA.TURBONID.E.* <strong>Marine</strong>.a. Aperture ovate, inner-lip formed by the body-whorl on which theperistome is spread.b. Pillar-lip simple, or without teeth.c Peristome incomplete retrally.Turbo.Phasianella.Turritella.aa.cc.Peristome complete retrally.Cingula.bb. Pillar-lip with a tooth.Odostomia.Monodonta.Aperture circular, peristome entire, and more or less disjoined fromthe body-whorl.b. Whorls with transverse ridges, the last formed one constituting athickened margin to the mouth.Scalaria.bb.Cyclostrema.Whorls destitute <strong>of</strong> the transverse ridges, forming, in succession,the peristome.c. Shell armed with tubercles or processes.Delphinula.Cirus.cc.Shell destitute <strong>of</strong> processes.Skenea.Ettomphalus.** Fluviatile.a. Peristome entire.Paludina.Ampullaria.b. Peristome incomplete retrally.Melania.

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