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The siliceous shell of a diatom. It is composed of two valves, one overlapping the other, like a pill box and its cover.

One of the subclasses of fishes. They have an arterial cone and bulb, spiral intestinal valve, and the optic nerves united by a chiasma. Many of the species are covered with bony plates, or with ganoid scales; others have cycloid scales.

A door, valve, or other device, for stopping the passage of water through a dam, lock, pipe, etc.

rtion of an engine or machine is transmitted to another, considered collectively; as, the valve gearing of locomotive engine; belt gearing; esp., a train of wheels for transmitting and varying motion in machinery. Frictional gearing. See under Frictional. -- Gearing chain, an endless chain transmitted motion from one…

ant brothers; a giant son. Giant cell. (Anat.) See Myeloplax. -- Giant clam (Zoöl.), a bivalve shell of the genus Tridacna, esp. T. gigas, which sometimes weighs 500 pounds. The shells are sometimes used in churches to contain holy water. -- Giant heron (Zoöl.), a very large African heron (Ardeomega goliath). It is t…

r heads (Cynara Scolymus); also, certain species of the related genus Echinops. -- Globe valve. (a) A ball valve. (b) A valve inclosed in a globular chamber. Knight.

water and spread on shells, for artists' use; -- called also gold paint. (b) (Zoöl.) A bivalve shell (Anomia glabra) of the Atlantic coast; -- called also jingle shell and silver shell. See Anomia. -- Gold size, a composition used in applying gold leaf. -- Gold solder, a kind of solder, often containing twelve parts…

A large, handsome, marine, univalve shell (Triton femorale).

A football field. Gridiron pendulum. See under Pendulum. -- Gridiron valve (Steam Engine), a slide valve with several parallel perforations corresponding to openings in the seat on which the valve moves.

One of the whorls of a spiral univalve shell. Center of gyration. (Mech.) See under Center. -- Radius of gyration the distance between the axis of a rotating body and its center of gyration. Rankine.

ering it when cold. -- Hammer shell (Zoöl.), any species of Malleus, a genus of marine bivalve shells, allied to the pearl oysters, having the wings narrow and elongated, so as to give them a hammer-shaped outline; -- called also hammer oyster. -- To bring to the hammer, to put up at auction.

Any wheel worked by hand; esp., one the rim of which serves as the handle by which a valve, car brake, or other part is adjusted.

A genus of marine univalve shells; the harp shells; -- so called from the form of the shells, and their ornamental ribs.

promys, Plagiodon, and allied genera. -- Hedgehog shell (Zoöl.), any spinose, marine, univalve shell of the genus Murex. -- Hedgehog thistle (Bot.), a plant of the Cactus family, globular in form, and covered with spines (Echinocactus). -- Sea hedgehog. See Diodon.

Spiral; curved, like the spire of a univalve shell.

. Called also soldier crab. The hermit crabs usually occupy the dead shells of various univalve mollusks. See Illust. of Commensal. -- Hermit thrush (Zoöl.), an American thrush (Turdus Pallasii), with retiring habits, but having a sweet song. -- Hermit warbler (Zoöl.), a California wood warbler (Dendroica occidentali…

A division of bivalve shells, including the marine mussels, in which the two adductor muscles are very unequal. See Dreissena, and Illust. under Byssus.

A fossil bivalve mollusk of the genus Hippurites, of many species, having a conical, cup-shaped under valve, with a flattish upper valve or lid. Hippurites are found only in the Cretaceous rocks.

Having an entire aperture; -- said of many univalve shells.

A division of phyllopod Crustacea, including those that are entirely covered by a bivalve shell.