tetrahedron 
tlnguisherl by having nn orthocenter. Polar tetrahe- 
dron, a tetrahedron the planes of which are tlu- polars of 
the vertices of another tetrahedron. Tetrahedron Of 
MbbiUSjOiie of a pair of tetrahcilra each inscribed in the 
oilier. -Truncated tetrahedron, a solid formed i..v cut- 
tin : ol! r:irli enniri of a tetrahedron l>y a plane parallel to 
'I ..... pji.isile laee to BUell HIl extent as In leave tllO faCCS 
regular hexagons. At the truncated purtH there areregn- 
l;n triangles. II i.s one of the thirteen Archimedean solids. 
tetrabezahedral (tot-ra-hok-sa-he'dral), a. [< 
tetrphexakedron + -<il.] Having the form of a 
t etni In '.\:i lii 'droii. Also tetrakignexokedral. 
tetrahexahedron (tot-ra-liok-.sa-he'dron), . [< 
^ iiv. nr/xi-, four, + tf, six, + 
different possibilities 
fi'pn, seat, base (see .. K/.- 
/Iron).] A solid bounded by 
twenty-four equal triangular 
faces, four corresponding to 
each face of the cube. In crys- 
tallography this solid belongs to 
the Isometric system. In geometry 
the name is especially applied to 
that variety in which all the adja- 
cent faces are equally inclined to 
one another. Also called tetrakixhfxahcdrun, and some- 
times fluoroid, as being a form common with fluor-spar, 
tetrakishexahedron (tet'ra-kis-hek-sa-he'- 
ilron). n. [< Gr. rerpdmf, rerpam, four times, + 
10. lir.m/icilron.] Same as tetrahexahedron. 
tetralemma (tet-ra-lem'a), n. [< Gr. rerpa-, 
four, + ty/i/M, a proposition: see lemma.] A 
dilemma in which four differ 
are considered, 
tetralogy (te-tral'o-ji i. ii. [= V. tftniliniii; < 
Gr. rerpa)M-yia, a group of four dramas, < TIT/HI-, 
four ; + Xoxof, speech.] A group of four dra- 
matic compositions, three tragic and one sa- 
tyric, which were exhibited in connection on 
the Athenian stage for the prize at the festi- 
vals of Bacchus. The term has been extended to a 
group of four operatic works treating of related themes, 
and intended to be performed in connection, 
tetralophodont (tet-ra-lof'6-dout), a. [NL., 
(. Gr. rerpa-, four, + /o^of, ridge, + o<iorf (orfovr-) 
= E. tooth.] Having that dentition which is 
characteristic of the true mastodons, whose 
molars are four-ridged. 
tetramastigate (tet-ra-mas'ti-gat), a. [< Gr. 
rerpa-, four, + /laoril- (fiaorty-), a whip, + -ate 1 .] 
Having four flagella, as an infusoriau. 
Tetrameles (te-tram'e-lez), H. [NL. (Robert 
Brown, 18126), from its 4-merous flowers; < Gr. 
riroa, four, 4- /'/nf, a limb, member.] A ge- 
nus of plants, of the order Datiscete, charac- 
terized by apetalous dio>cious flowers, with four 
calyx-lobes and four elongated stamens or four 
styles.- The only species, T. midijiora, Is a native of 
India, Ceylon, and .lava. It is a tall tree the only tree 
in an otherwise entirely herbaceous order; it bears broad 
long-petioled deciduous leaves, preceded by numerous 
small flowers in long and slender panicled racemes. It is 
known in India && jungle-bendy, and in Java as icetiwng- 
tree. 
Tetramera (te-tram'e-ra), n. pi. [NL., neut. 
pi. of tetramerus : see tetntmrrous.] Inentom.: 
(a) In Latreille's system, 
a division of Coleoptern, 
containing those beetles 
all of whose tarsi are 
usually or apparently 
tetramerous or four- 
jointed. Also called 
Cryptopcntamera and 
Pseudotetramera. (b) A 
prime division of the 
iiymenopterous family 
Clialriiliilir, comprising 
six subfamilies in which rf"gedtani of other 7V>" 
the tarsi are four-jointed. 
tetrameral (te-tram'e-ral), a. [< tetramcr-oiis 
+ -al.] Four-parted; having parts in fours; 
t rtramerous, as a polyp ; of or pertaining to the 
Trtrameratiii. 
Tetrameralia (te-tram-e-ra'li-a), n. pi. [NL. : 
sci' tstrttmaral.] The tetrameral polyps, as a 
subclass of scyphotnedusans distinguished from 
()ctonirr<iliii, and composed of the three orders 
Ctili/ci>:<>n. 1'irnmi'diixx, and Cubomedusee. 
tetramerism (te-tram'e-rizm), . [< tetram- 
rr( <>.*) + -imii.] In :ool. and hot., division into 
four parts, or the state of being so divided: 
four-pnrtodiu'ss. Amrr. \dt., XXII. 941. 
tetramerous (te-tram'e-rus), a. [< NL. te- 
trumi-rux, < Gr. rerpauepfc, four-parted, < rerpa-, 
four, + uepof, part.] Consisting of or divided 
into four parts; characterized by having four 
parts. Specincally~() In 6o.,having the parts in fours: 
as, a Mrameroui flower (that is, one having four members 
in each of the floral whorls). It is frequently written 4- 
inermu. (b) In zoiil.: (1) Four-parted: especially noting 
an actinozoan having the radiating parts or organs ar- 
ranged in fours or multiples of four. Compare htxam- 
erma. (i) In entomology, having four joints, as the tar- 
393 
I. I a 
itnxiiicta ; 3, 
6367 
BUS of an insect ; having four-jointed tarsi, as a hectic or 
chalcld ; of or pertaining to the7Vfrarru>rrt. see cuts nndei 
PJtytOJRMda and '/' tunitpra. 
tetrameter (ii'-tram'e-ter), . and n. [< LL. te- 
h'limi ti-iiH, < (Jr. riT/iii/iir/inf, having four mea- 
sures, neut. nrp&fitrpav, a verse of four mea- 
sures, < nrpa-, four, + /tirpov, measure.] I. n. 
Having four measures. 
II. a. In iii'os., a verse or period consisting 
of four measures. A trochaic, Iambic, or anapestic 
tetrameter consists of four dipodies (eight feet). A te- 
trameter of other rhythms is a tctrapody, or period of 
four feet. The name is specifically given to the trochaic 
tetrameter cataloctlc. An example of the acatalectlc te- 
trameter is 
(luce upon ft | midnight dreary, I as I pondered | weak 
and weary. Pae, The Raven. 
tetramorph (tet'ra-morf ), H. [< Gr. rerpa/io/xfof, 
four-shaped, fourfold, < rerpa-, four, + popQ'/, 
form.] In t'liri.ttiini art, the union of the four 
attributes of the evangelists in one figure, 
winged, and standing on winged fiery wheels, 
the wings being covered with eyes. It is the 
type of unparalleled velocity. Fairliolt. 
tetrander (te-tran'der), n. [< Gr. rerpa-, four, 
+ avijp (avSp-), male (in mod. bot. a stamen).] 
In hot., a monocli- 
nous or hermaphro- 
dite plant having 
four stamens. 
Tetrandria (te- 
tran'dri-ft), n, pi. 
[NL. : see tetran- 
drr.] The fourth 
class of plants in 
the Linnean sys- 
tem,comprehending 
such as have four 
stamens. The orders 
belonging to this class T <tr<,<tri.- 
are Monof/ynia, Jhrjynut, 
Tetrayynia. The teazel, dodder, and pond-weed are ex- 
amples. 
tetrandrian (te-tran'dri-an), a. [< tetrander + 
-ian.] In bot., belonging to the class Tetran- 
dria ; tetrandrous. 
tetrandrous (te-tran'drus), a. [< tetrander + 
-ous.] In hot., having four stamens; charac- 
teristic of the class Tetrandria. 
tetrant (tet'rant), n. [< Gr. rerpa-, four, + 
-ant.] A quadrant. IFcale. [Rare.] 
Tetranychidse (tet-ra-nik'i-de), n. pi. [NL., 
< Tetratiychu* + -idle.] A family of mites, 
containing those forms known as spinning- 
mites, and founded on the genus Tetrant/chux. 
In common with the Trambidiidx or harvest-mites, the 
Tetranycliidsf have an appendiculate terminal palpal 
joint, but are smaller and more highly colored than the 
harvest-mites, and are plant-feeders exclusively. Next to 
Tetranychu*, Bryobia is the most noticeable genus. B. 
pratt'iutis frequently enters houses in the United States in 
enormous numbers in the fall. 
Tetranychus (te-tran'i-kus), n. [NL. (Dufour, 
1832), prop. Tetraonychus, < Gr. rerpa-, four, + 
6vv (otn'x-), claw.] A very large and wide- 
spread genus of spinning-mi tes,havinglegs with 
seven joints, the feet short and curved, and the 
mouth with a barbed sucking-apparatus. It con- 
tains minute yellowish or reddish species, most of which 
spin more or less of a web on the under side of leaves, 
and are noted as injurious to vegetation. The so-called 
red-spider, a cosmopolitan hothouse pest, is T. lelarius. 
Tetrao (tet'ra-o), n. [NL., < L. tetrao, < Gr. 
rerpduv, a pheasant, a grouse.] The leading ge- 
nus of Tetraonidx, formerly including all the 
grouse, but subsequently variously restricted, 
now to the capercaillie, T. urogallus, and some 
closely related species. See cut under 
caillie. 
Tetrapleura 
snow-partridge (tee Z^rm) ; they are Indifferently known 
as maw-phfOMnti, iiuite-cixla, and tnow-chvliori, one of 
them ti ing also specified as the clion/' T. cas- 
pius; three other xpeciesare named 7'. hiinalaueiin*, T. 
allaicuf, and T. tiljrtamu. The whole i genus 
Is from Asia Minor to western China, but only in mountain- 
ranges at altitudes up to l>,im feet. In some respects 
the genus approaches Tetraophatit (which see). The size 
is large, the male*, attaining a length of two feet or mot.- ; 
the sexes are nearly alike in plumage, which Is of varied 
dark coloration. The birds frequent open rocky places, 
generally In flocks, and nest on the ground, laying 6 to II 
eggs of an olive color with reddish spots. Also called 
Chourtlca. 
tetraqnid (tet'ru-o-nid), a. and . I. a. Of or 
pertaining to tho Tftrnniiiiln , or grouse family. 
II. n. Any grouse, or other member of the 
Trtr<tn>iid&. 
Tetraonidae (tet-ra-on'i-de). n.pl. [NL., < Tet- 
rao( n-) + -idx.] A family of gallinaceous birds, 
of the order (lulling, of which the type is the 
genus Tetrao; the grouse family, having the 
tarsi and nasal fosste more or less completely 
feathered. The leading genera besides Tetrao are Ly- 
mna, Canact (or Dcndragapug), Falcipennit, LayojMi, Cen- 
trocercwt, I'edicecctfjt, Cupidonia (or Tjftnpanuchwt), and 
RonaMt. They are confined to the northern hemisphere, 
and include, besides the birds usually called grmae, the 
capercaillie, prairie-hen, sage-cock, ptarmigan, and others. 
The family has been used in a more comprehensive sense, 
including then an indefinite number of genera of par- 
tridges, quails, and similar birds. See cuU under black- 
cock, Botiasa, Canaff, capercailzie, Centrocemu, Cupidonia, 
grmue, Oreortyx, partridge, Pedioecetts, &n& ptarmigan. 
Tetraoninae (tefra-o-ni'ne), n.pl. [NL., < 
Tetrao(n-), a grouse, H- -inte.] The grouse fam- 
ily, Tetraonidx, rated as a subfamily of gallina- 
ceous birds, or a restricted division of that fam- 
ily in its widest sense. 
tetraonine (tet'ra-o-nin), a. Of or pertaining 
' to the Tetraoninse. ' 
The true (lallinic offer two types of structure, "one of 
which may be called Galllne, and the other Trtranninf." 
Eneyc. Brit., XVIII. 838. 
Tetraonomorphae (tet"ra-o-no-m6r'fe), n. pi. 
[NL., < Gr. Ttrpauv, a grouse, + /iop<t>r/, form.] 
In Sundevall's system of ornithological clas- 
sification, a cohort of Gallinse, consisting of the 
sand-grouse (I'teroclidse) and grouse proper 
(Tetraonidx). 
Tetraonychidae, Tetraonychus. More correct 
forms of Tetranycltidie, Tetranychux. 
Tetraoperdix (tet'ra-o-per'diks), n. [NL.,< tr. 
rerpAui; a grouse, + Trfpfif, a partndge.] In 
tetraodion (tet-ra-6'di-on), w. [< MGr. rerpa- 
<f6iav, < Gr. rerpa-, four, + ^xJi;, ode.] In the 
fir. Ch., a canon of four odes. 
Tetraodon, tetraodont, etc. See Tetrodon,etc. 
Tetraogallus (tet'ra-o-gal'us), . [NL. (J. E. 
Gray, 1833-4), < L. tetrao, a grouse, + gallus, 
cock.] A genus of snow-partridges. These birds 
are near relatives of Lerva nivicola, another species of 
Snow.partridgc ( Tetrttogalltts kimalaytnsis'*. 
ornith., same as Lerva. 
Tetraophasis (tet-ra-of'a-sis), n. [NL. (Jules 
Verreaux, 1870), < Gr. rerpduv, a grouse, + Qaotf, 
the river Phasis, with ref. to jtmfftf, pheasant: 
see pheasant.] A ^enus of gallinaceous birds 
peculiar to Tibet, with one species, T. obscurus, 
in some respects intermediate between pheas- 
ants and grouse. It is about 20 inches long, 
and of dark-brown and -gray colors, alike in 
both sexes. 
tetrapetalous (tet-ra-pet'a-lus), a. [< Gr. 
rerpa-, four, + Tnfro/lov, leaf (petal).] In bot., 
having four petals. 
tetrapnarmacon (tet-ra-far'ma-kon), n. [NL., 
a\sotetrapharmacum; < Gr. Terpa^dpftoKov, a com- 
pound of wax, resin, lard, and pitch, neut. of re- 
rpa<l>Ap/iaKof, compounded of four drugs, < rerpa-, 
four, + Q&piioKav, drug : see pharmacon.] An 
ointment composed of wax, resin, lard, and 
pitch. 
tetrapharmacum(tet-ra-far'ma-kum), n. Same 
as telrapharmariin. 
tetraphony(tet'ra-fo-ni), . [< Gr. m-pa-, four, 
+ 0uii>/, voice.] In early medieval music, di- 
aphony for four voices. 
Tetrap'hyllidea (tet'ra-fi-lid'e-a), w. pi. [NL. , 
< Gr. Tfrpa-, four, + Qifaov, a leaf.] A division 
of Cestoidea, including tapeworms of various 
fishes, in which the head is furnished with four 
lobes, suckers, or tentacles, or in any way dis- 
tinguished by fours into sets of parts or organs. 
The group includes the genera Tetrarhynchtit, 
Echineibothrium, and Acantliobothrium. 
tetraphyllidean (tet'ra-fi-lid'e-an), a. Of or 
belonging to the Tetraphi/llided. " 
tetraphyllous (tet-ra-fiT'us), a. [< Gr. rerpa-. 
four, + ^;//or, a leaf.] In bot., four-leaved ; 
consisting of four distinct leaves or leaflets. 
Tetrapla (tet'ra-pla), n. [< Gr. rtrpaT^o, neut. 
El. of rtrpairUof, rtrpairAwf, fourfold, < rerpa-, 
>ur, + -!r?opc, -fold.] An edition of the Bible 
in four versions. The name is specially given to a 
work by Origen, containing the Greek versions of Aquila, 
Symmachus, and Theodotion and the Septuaglnt Com- 
pare Htxapla, Octapla. 
Tetrapleura (tet-ra-plo'ra). H. pi. [NL., < Gr. 
rerpa-, four. + -/n/m\ a rib.] Those organic 
forms which are tetrapleural : distinguished 
from IHplrnrn. 
