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ontal water wheel, usually in the form of a short cylinder, to the circumference of which spiral vanes or floats, placed radially, are attached, turned by the impact of one or more streams of water, conducted so as to strike against the floats in the direction of a tangent to the cylinder.

A more or less cylindrical, and often spiral, case secreted or constructed by many annelids, crustaceans, insects, and other animals, for protection or concealment. See Illust. of Tubeworm.

The whole set of whorls of a spiral shell.

Rolled in a spiral; scroll-like; turbinate; -- applied to the thin, plicated, bony or cartilaginous plates which support the olfactory and mucous membranes of the nasal chambers.

Whirling in the manner of a top. A spiral and turbinated motion of the whole. Bentley.

Any one of several large, thick, spiral marine shells belonging to Rapa and allied genera, somewhat turnip-shaped.

attened on the upper side and often ornamented by spines or tubercles; -- said of certain spiral shells.

Any fossil ammonite of the genus Turrilites. The shell forms an open spiral with the later whorls separate.

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.

To ascend in spiral lines about a support; to climb spirally; as, many plants twine.

The act of one who, or that which, twines; (Bot.) the act of climbing spirally.

To contort; to writhe; to complicate; to crook spirally; to convolve. Twist it into a serpentine form. Pope.

Contorted; crooked spirally; subjected to torsion; hence, perverted. Twisted curve (Geom.), a curve of double curvature. See Plane curve, under Curve. -- Twisted surface (Geom.), a surface described by a straight line moving according to any law whatever, yet so that the consecutive positions of the line shall not be…

A drum-shaped wheel with spirally curved partitions by which water is raised to the axis when the wheel revolves with the lower part of the circumference submerged, -- used for raising water, as for irrigation.

A depression or opening in the center of the base of many spiral shells.

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

nequally; bellied; ventricular; as, a ventricose corolla. Ventricose shell. (Zoöl.) (a) A spiral shell having the body whorls rounded or swollen in the middle. (b) A bivalve shell in which the valves are strongly convex.

onging 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.

ecies of small land snails belonging to the genus Vertigo, having an elongated or conical spiral shell and usually teeth in the aperture.

have lost their intervening partitions, and are usually marked with dots, pits, rings, or spirals by internal deposition of secondary membranes; a duct. Acoustic vessels. See under Acoustic. -- Weaker vessel, a woman; -- now applied humorously. "Giving honor unto the wife, as unto the weaker vessel." 1 Peter iii. 7. "…