Part 331

Rho"don*ite (?), n. [Gr. "ro`don the rose. ] (Min.) Manganese spar, or silicate of manganese, a mineral occuring crystallised and in rose-red masses. It is often used as an ornamental stone.

Rho"do*phane (?), n. [Gr. "ro`don the rose + &?;&?;&?; to show.] (Physiol.) The red pigment contained in the inner segments of the cones of the retina in animals. See Chromophane. W. KÜhne.

Rho*dop"sin (?), n. [Gr. "ro`don rose + "w`ps eye.] (Physiol.) The visual purple. See under Visual.

Rho"do*sperm (?), n. [Gr. "ro`don the rose + spe`rma a seed.] (Bot.) Any seaweed with red spores.

As the name of a subclass, Rhodosperms, or Rhodospermeæ, is synonymous with Florideæ (which see.)

Rhomb (?), n. [L. rhombus, Gr. &?;&?;&?; rhomb, a spinning top, magic wheel, fr. &?;&?;&?; to turn or whirl round, perhaps akin to E. wrench: cf. F. rhombe. Cf. Rhombus, Rhumb.] 1. (Geom.) An equilateral parallelogram, or quadrilateral figure whose sides are equal and the opposite sides parallel. The angles may be unequal, two being obtuse and two acute, as in the cut, or the angles may be equal, in which case it is usually called a square.

2. (Geom.) A rhombohedron.

Fresnel's rhomb (Opt.), a rhomb or oblique parallelopiped of crown or St. Gobain glass so cut that a ray of light entering one of its faces at right angles shall emerge at right angles at the opposite face, after undergoing within the rhomb, at other faces, two reflections. It is used to produce a ray circularly polarized from a plane-polarized ray, or the reverse. Nichol.

Rhom"bic (?), a. 1. Shaped like a rhomb.

2. (Crystallog.) Same as Orthorhombic.

Rhom`bo*ga"noid (?), n. [Rhomb + ganoid.] (Zoöl.) A ganoid fish having rhombic enameled scales; one of the Rhomboganoidei.

||Rhom`bo*ga*noi"de*i (?), n. pl. [NL.] (Zoöl.) Same as Ginglymodi.

Rhom"bo*gene (?), n. [Rhomb + root of Gr. &?;&?;&?; to be born.] (Zoöl.) A dicyemid which produces infusorialike embryos; -- opposed to nematogene. See Dicyemata. [Written also rhombogen.]

Rhom`bo*he"dral (?), a. (Geom. & Crystallog.) Related to the rhombohedron; presenting the form of a rhombohedron, or a form derivable from a rhombohedron; relating to a system of forms including the rhombohedron and scalenohedron.

Rhombohedral iron ore (Min.) See Hematite. -- Rhombohedral system (Crystallog.), a division of the hexagonal system embracing the rhombohedron, scalenohedron, etc.

Rhom`bo*hed"ric (?), a. (Geom. & Crystallog.) Rhombohedral.

Rhom`bo*he"dron (?), n. [NL., fr. Gr. &?;&?;&?; rhomb + &?;&?;&?; seat, base.] (Geom. & Crystallog.) A solid contained by six rhomboids; a parallelopiped.

Rhom"boid (rm"boid), n. [Gr. &?;&?;&?; rhomboidal; &?;&?;&?; rhomb + e'i^dos shape: cf. F. rhomboïde.] (Geom.) An oblique-angled parallelogram like a rhomb, but having only the opposite sides equal, the length and with being different.

Rhom"boid (rm"boid), a. Same as Rhomboidal.

Rhom*boid"al (?), a. [Cf. F. rhomboïdal.] Having, or approaching, the shape of a rhomboid.

Rhom*boid"es (?), n. A rhomboid. [R.] Milton.

Rhom`boid-o"vate (?), a. Between rhomboid and ovate, or oval, in shape.

Rhomb" spar` (?). (Min.) A variety of dolomite.

Rhom"bus (?), n. [L.] Same as Rhomb, 1.

Rhon`chal (?), a. (Med.) Rhonchial.

Rhon"chi*al (?), a. (Med.) Of or pertaining to a rhonchus; produced by rhonchi.

Rhonchial fremitus. [L. fremitus a dull roaring or murmuring.] (Med.) A vibration of the chest wall that may be felt by the hand laid upon its surface. It is caused in the production of rhonchi in the bronchial tubes.

Rhon*chis"o*nant (?), a. [L. rhonchus a snoring + sonans, p. pr. of sonare to sound.] Making a snorting noise; snorting. [R.]