(Te*thy"dan) n. [See Tethys.] (Zoöl.) A tunicate.
(||Te`thy*o"de*a) n. pl. [NL., fr. Tethys + Gr. form.] (Zoöl.) A division of Tunicata including
the common attached ascidians, both simple and compound. Called also Tethioidea.
(Te"thys) n. [NL., fr. Gr. an oyster, or a kind of ascidian.] (Zoöl.) A genus of a large naked mollusks
having a very large, broad, fringed cephalic disk, and branched dorsal gills. Some of the species become
a foot long and are brilliantly colored.
(Tet"ra-) [Gr. te`tra-, from te`sares, te`ttares, four. See Four.]
1. A combining form or prefix signifying four, as in tetrabasic, tetrapetalous.
2. (Chem.) A combining form (also used adjectively) denoting four proportional or combining parts of
the substance or ingredient denoted by the term to which it is prefixed, as in tetra-chloride, tetroxide.
(Tet`ra*bas"ic) a. [Tetra- + basic.] (Chem.) Capable of neutralizing four molecules of a
monacid base; having four hydrogen atoms capable of replacement by bases; quadribasic; said of certain
acids; thus, normal silicic acid, Si(OH)4, is a tetrabasic acid.
(Tet`ra*bor"ic) a. [Tetra- + boric.] (Chem.) Same as Pyroboric.
(||Tet`ra*bran`chi*a"ta) n. pl. [NL. See Tetra-, and Branchia.] (Zoöl.) An order of Cephalopoda
having four gills. Among living species it includes only the pearly nautilus. Numerous genera and species
are found in the fossil state, such as Ammonites, Baculites, Orthoceras, etc.
(Tet`ra*bran`chi*ate) a. [Tetra + branchiate.] (Zoöl.) Of or pertaining to the Tetrabranchiata.
n. One of the Tetrabranchiata.
(Tet`ra*car"pel) a. [Tetra- + carpellary.] (Bot.) Composed of four carpels.
(Tet"ra*chord) n. [L. tetrachordon, Gr. from four-stringed; te`tra- (see Tetra-) + a chord: cf.
F. tétrachorde.] (Anc. Mus.) A scale series of four sounds, of which the extremes, or first and last,
constituted a fourth. These extremes were immutable; the two middle sounds were changeable.
(Tet`ra*chot"o*mous) a. [Gr. te`tracha in four parts + te`mnein to cut.] (Bot.) Having
a division by fours; separated into four parts or series, or into series of fours.
(Tet*rac"id) a. [Tetra + acid.] (Chem.) Capable of neutralizing four molecules of a monobasic
acid; having four hydrogen atoms capable of replacement ba acids or acid atoms; said of certain bases; thus,
erythrine, C4H6(OH)4, is a tetracid alcohol.
(Tet`ra*coc"cous) a. [See Tetra-, and Coccus.] (Bot.) Having four cocci, or carpels.
(Tet`ra*co"lon) n. [Gr. with four members; te`tra- (see Tetra-) + limb, member.] (Pros.) A
stanza or division in lyric poetry, consisting of four verses or lines. Crabb.
(||Te`tra*co*ral"la) n. pl. [NL. See Tetra-, and Corallum.] (Paleon.) Same as Rugosa.
(Te*trac`ti*nel"lid) n. (Zoöl.) Any species of sponge of the division Tetractinellida. Also
(||Te*trac`ti*nel"li*da) n. pl. [NL., from Gr. te`tra- tetra- + ray, spoke.] (Zoöl.) A division
of Spongiæ in which the spicules are siliceous and have four branches diverging at right angles. Called