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A genus of marine gastropods having a long, tapering spire. They belong to the Toxoglossa. Called also auger shell.

A division of marine gastropod mollusks in which the radula are converted into poison fangs. The cone shells (Conus), Pleurotoma, and Terebra, are examples. See Illust. of Cone, n., 4, Pleurotoma, and Terebra.

An extensive artificial group of gastropods comprising all those which have a spiral shell and the foot attached to the base of the neck.

Any one of many species of marine gastropods belonging to Triton and allied genera, having a stout spiral shell, often handsomely colored and ornamented with prominent varices. Some of the species are among the largest of all gastropods. Called also trumpet shell, and sea trumpet.

A group of gastropod mollusks having a tubular shell. Vermetus is an example.

A genus of large marine gastropods having a thick heavy shell with conspicuous folds on the columella.

Any one of numerous marine gastropods of the genus Turbo or family Turbinidæ, usually having a turbinate shell, pearly on the inside, and a calcareous operculum.

Any spiral marine gastropod belonging to Turritella and allied genera. These mollusks have an elongated, turreted shell, composed of many whorls. They have a rounded aperture, and a horny multispiral operculum.

Any marine tectibranchiate gastropod of the genus Umbrella, having an umbrella-shaped shell; -- called also umbrella shell. Umbrella ant (Zoöl.), the sauba ant; -- so called because it carries bits of leaves over its back when foraging. Called also parasol ant. -- Umbrella bird (Zoöl.), a South American bird (Cephalop…

h are used in medicine. -- Unicorn shell (Zoöl.), any one of several species of marine gastropods having a prominent spine on the lip of the shell. Most of them belong to the genera Monoceros and Leucozonia.

- in part equivalent to uniformitarianism, but also used, more broadly, as opposed to catastrophism.

Same as Gastropoda.

A genus of small spiral fresh-water gastropods having an operculum.

Any fresh-water gastropod of the genus Valvata.

A genus including several species of large marine gastropods having massive pyriform shells, with conspicuous folds on the columella.

Any larval gastropod or bivalve mollusk in the state when it is furnished with one or two ciliated membranes for swimming.

Any one of several species of marine gastropods belonging to Velutina and allied genera.

Any one of many species of marine gastropods belonging to Vermetus and allied genera, of the family Vermetidæ. Their shells are regularly spiral when young, but later in life the whorls become separate, and the shell is often irregularly bent and contorted like a worm tube.

A genus of terrestrial gastropods, having transparent, very thin, and delicate shells, -- whence the name.

d. -- Viviparous shell (Zoöl.), any one of numerous species of operculated fresh-water gastropods belonging to Viviparus, Melantho, and allied genera. Their young, when born, have a well-developed spiral shell.