isomorphous 
dron varying from 105 to 107. Between the members 
of an isomorphous group intermediate compounds may 
occur, regarded as isomorplious mixtures of the two un- 
like molecules. Thus, dolomite, the carbonate of calcium 
and magnesium, may be considered as formed by the 
union of the calcium carbonate molecules with those of 
magnesium carbonate. (&) pi. In math. See groups. 
Isomya (i-so-mi'a), n. pi. [NL., < Gr. iaos, 
equal, + /jvf, a mouse, a muscle, = E. mouse. 
Cf. Dimyaria.] Isomyarian mollusks; Dimy- 
aria proper, one of three orders into which la- 
mellibranchs have been divided : distinguished 
from Heteromya and Monomya. They are di- 
vided into Integropallia and Sinupallia. 
isomyarian (r''so-ini-a'ri-an), a. [< Isomya + 
-arian.] Having two adductor muscles of the 
same size or nearly so, as most bivalve mol- 
lusks ; perfectly dimyarian ; of or pertaining to 
the Isomya. 
ison (i'son), n. [< Gr. iaov, neut. of laof, equal: 
see iso-.] In the music of the Greek Church, 
the sign for the key-note. 
Isonandra (i-so-uan'dra), n. [NL., irreg. < Gr. 
rof, eq"ual, + avr/p (avdp-), male (mod. bot. sta- 
men).] A small genus of gamopetalous plants, 
of the natural order Sapotacece. The flowers are 
tetramerous, the corolla-tube is elongated, the stamens are 
8 in number and nearly equal, and the seeds are albumi- 
nous. They are evergreen trees with entire leaves, na- 
tives of southern India, Ceylon, and the adjacent islands. 
The species of this genus, particularly /. polyantha and 
/. obovata, yield a good quality of gutta-percha. /. Gutta, 
the true gutta-percha, is now referred to the genus Pala- 
quium. Wight, 1840. 
Isonandreae (i-so-nan'dre-e), n. pi. [NL. 
(Eadlkofer, 1887),'< Isonandra + -ea.] A tribe 
of plants of the natural order Sapotacece, con- 
taining the genera Isonandra and Payena. 
isonephelic (I"so-ne-f el'ik), a. [< Gr. lao; , equal, 
+ VCIJI^TI, cloud : see nebula.] Indicating equal- 
ity as regards the prevalence of clouds Isone- 
pnellc line, in meteor., an imaginary line over the earth's 
surface passing through points which have the same de- 
gree of cloudiness of the sky for a given period (month or 
year). 
A chart of the world showing lines of equal annual 
cloudiness (isonephelic) is given by Kenan. 
Smithsonian Report, 1881, p. 290. 
isonomia (i- so -no 'mi -a), . [< Gr. inovofiia, 
equality of rights : see isonomy.] Equality be- 
fore the law ; uniformity of rights. 
There is no part of our constitution so admirable as this 
Blind Isopod (Cacidotea stygia). Mai 
Cave, Kentucky. 
equality of civil rights, this isonomia which the philoso- 
phers of ancient Greece only hoped to find in democrati- 
cal government. Sir E. Creasy, Eng. Const., p. 200. 
isonomic (i-so-nom'ik), a. [< Gr. laovo/ui<6f, < 
\aovofiia, equality of laws: see isonomy.] 1. 
Of or pertaining to isonomy ; the same or equal 
in law or right. 2. One in kind or origin : spe- 
cifically applied in chemistry to isomorphism 
subsisting between two compounds of like com- 
position : opposed to heteronomic. 
isonomy (i-son'o-mi), n. [< Gr. laovofda, equal 
distribution, equality of rights or laws, < taovo- 
/tof, equally distributed, having equal rights, < 
laof, equal, + v6/u>$, distribution, custom, law: 
see name.] Equality as regards rights and priv- 
ileges ; isonomia. 
Philolaus . . . introduced an isonomy into the oligarchy, 
and so enabled it to hold its ground. 
Von Banks, Univ. Hist, (trans.), p. 135. 
(i'so-nim). n. [< Gr. iaaw/ios, having 
the same name, s icrof, equal, + dvo/ta, ovv/ia, 
name.] In philol., a paronym. 
isonymic (i-so-nim'ik), a. [< isonym + -ic.] In 
plitiol., paronymic. 
isonymy (i-son'i-mi), n. [< Gr. laum/iia, same- 
ness of name, < iaavv/toc, having the same name : 
see isonym.] Same as paronymy. 
isopathy (i-sop'a-thi), n. [< Gr. laof, equal, + 
Traftjf, suffering, 'disease.] The theory that dis- 
ease may be cured by the product of the disease, 
as smallpox by minute doses of variolous mat- 
ter ; also, the theory that a diseased organ may 
be cured by eating the same organ of a healthy 
animal. Both theories are, of course, absurd. 
isoperimetrical (I-so-per-i-met'ri-kal), a. [< 
isoperimetry + -ie-al] 1. Of or pertaining to 
isoperimetry. 2. Having equal boundaries: 
as, isoperimetrical figures or bodies. 
isoperimetry (!"so-pe-rim'e-tri), n. [< Gr. laoc, 
equal, + ireplftsTpov, circumference : see perim- 
eter.] In geom., the science of figures having 
equal perimeters or boundaries. The problem to 
determine among all curves having their extremities at 
two given points and a given length that one which in- 
closes the maximum area is the problem of isoperimetry ; 
and the name is extended to every problem involving the 
calculus of variations in the same way. 
isopetalous (i-so-pet'a-lus), a. [< Gr. icro?, equal, 
+ Trfra/W, a leaf (petal): see petal.] Having 
equal petals. Thomas, Med. Diet. 
3198 
isophorous (I-sof 'o-rus), a. [< Gr. 
bearing or drawing equal weights, equal in 
strength, < i<rof, equal, + </>epeiv = E. bear*.] In 
bot., an epithet used by Liudley to express the 
relation to a species of its abnormal forms when 
they are sufficiently habitual to have been taken 
for distinct plants. Thus, the assumed genus 
of orchids Aclinia is now regarded as an isopho- 
rous form of Dendrobium. 
isopiestic (i'so-pi-es'tik), a. [< Gr. laof, equal, 
+ jTOtrrdf, verbal adj. of mifriv, press, squeeze.] 
Isobaric ; denoting equal pressure. 
Isopleura (i-so-plo'ra), n.pl. [NL., neut. pi. of 
isopleurus: see isopfeurous.] A prime division 
of gastropods containing those which are equal- 
sided or bilaterally symmetrical: contrasted 
with Anisoplewa. The isopleural gastropods are 
chiefly represented by the chitons, but also include such 
worm-like forms as Ckcetoderma and Neomenia. Rank- 
ed as a superorder, the Isopleura have been divided into 
three orders, Polyplacophora, Chcetodermce, and Ifeomenoi- 
dea. 
isopleural (i-so-plo'ral), a. [As isopleur-oits + 
-al.] Having the right and left sides equal; 
bilaterally symmetrical, as most animals; of or 
pertaining to the Isopleura. 
isopleurous (l-so-plo'rus), a. [< NL. isopleurus, 
< Gr. iadK^svpof, having equal sides, equilateral, 
< io-oc, equal, + nfavpa, side.] Same as isopleu- 
ral. 
Isoplexis (I-so-plek'sis), . [NL. (Lindley, 
1821), < Gr. jffof, equal, + irA^fjf, a stroke, < 
K^ijaaeiv, strike, cut.] A genus of Scrophu- 
larinece, closely allied to Digitalis, but distin- 
guished by a shrubby habit and by the fact 
that the upper lip of the corolla equals the 
lower. The two species, I. sceptrum from Madeira and 
I. Canariensis from the Canaries, cultivated in green- 
houses, bear terminal racemes of showy yellow or orange- 
colored flowers. 
isopod (i'so-pod), a. and . [< NL. isopus (iso- 
pod-), < Gr. 
tffof, equal, -f 
TTOL'f (iTO<5-) = 
E.foot.] I. a. 
Having the 
feet all alike, 
or similar in 
character; 
specifically, pertaining to the Isopoda or having 
their characters. Also isopodous. 
II. n. An isopod crustacean; any one of the 
Isopoda. 
Also isopodan, isopode. 
Isopoda (i-sop'o-da), n. pi. [NL., neut. pi. of 
isopus (isopod-Y, equal-footed: see isopod.] An 
order of arthrostracous or edriophthalmous 
(sessile-eyed) crustaceans, with 7 free thoracic 
somites bearing as many pairs of legs, which 
are alike in size and direction, whence the 
name; the Polygonata of Fabricius. The body 
is usually broad and depressed, and more or less arched ; 
the head is almost always distinct from the thorax, 
except from the first thoracic ring, with which it is 
united ; and the abdomen is short-ringed and often re- 
duced. There are no branchial thoracic vesicles, the 
respiratory function being carried on by the peculiarly 
modified laminar legs of the abdomen. The thoracic legs 
of the females may be modified to form brood-pouches for 
the eggs by means of delicate membranous plates called 
oogteyites. The 
sexes are distinct, 
except in Cymotho- 
id<e. Isopods are 
found in both salt 
and fresh water, 
and also on land. ^3&mk? <^^HHL^ 
The terrestrial iso- 
pods, family Onis- 
cidai, are known as 
sow-buffs, wood-lice, 
and slaters. The 
gribble, lAmnoria 
terebrans, is a ma- o^^ ,, , common wood-louse o 
nne form. Many sow-bujf : a, head ; 6, thorax ; c, abdomen. 
Isopoda are ecto- 
parasitic, as the Cymothoidce on the gills and in the mouth 
of fishes, and the BopyridtK in the gills of prawns. The or- 
der was divided by Milne-Edwards into three sections, Se- 
dentaria, Natatoria, and Cursoria, according to the hab- 
its of the animals. By Claus the Isopoda are made a sub- 
order of Arthrostraca, and divided into two tribes, Ani- 
sopoda (which resemble amphipods) and Euisopoda, or 
genuine isopods. Others reckon about ten families, not 
separated into suborders. Leading types are Tanaidce 
and Anceidte on the one hand, and on the other Cymo- 
thoidce, Spheeromidce, Idoteidx, Asellidce, Bopyridce, and 
Oniscidce. 
isopodan (i-sop'o-dan), a. and n. [< isopod + 
-an.] Same as isopod. 
The size of the body far transcends the ordinary Isopo- 
dan limit Encyc. Brit., VI. 659. 
isopode (i'so-pod), a. and n. Same as isopod. 
isopodiform (i-so-pod'i-form), a. [< NL. isopus 
(isopod-), isopod, + L. forma, form.] Formed 
isoseismic 
like an isopod ; resembling an isopod in form : 
specifically applied to six-footed, oblong, flat- 
tened larvse with a distinct thoracic shield, 
long antennre, and caudal bristles or plates, as 
those of the roaches. 
isopodimorphous (i-so-pod-i-m6r'fus), a. [< 
NL. isopus (isopod-), isopod, + Gr. i 
il, form.] 
Same as isopocliform. 
isopodous (i-sop'o-dus), a. [As isopod + -ous.] 
Same as isopod. 
iSOpOgonOUS (i-so-pog'o-nus), a. [< Gr. laof, 
equal, + iruyuv, beard, barb. ] Equally webbed : 
said of feathers whose inner and outer webs are 
alike in size and shape : opposed to anisopogo- 
nous. 
Three Types of Isopods. 
I, sedentary, Ropynts squillantm. a, na- 
tatory, Cymodocea lamarcki. 3, cursorial, 
Oniscits asellus. a common wood-louse or 
isopolity (i-so-pol'i-ti), n. [< Gr. 
equality of civic rights, < I<ro7ro/Urj?c, a citizen 
with equal rights, < iaof, equal, + ITO/UT^C, a 
citizen: see polity.] Equal rights of citizen- 
ship in different communities ; mutual politi- 
cal rights. 
Niebuhr . . . establishes the principle that the census 
comprehended all the confederate cities which had the 
right of isopolity. Milman. 
Between America and England . . . one would be glad 
if there could exist some isopolity. 
Clough, To C. E. Norton, Sept. 21, 1853. 
Isoptera (i-sop'te-ra), n. pi. [NL., neut. pi. of 
isopterns: seeisopterous.] The termites or white 
ants regarded as a suborder of Neuropter/i. 
They have large, equal, and naked wings not folded in re- 
pose, well-developed manducatory jaws, and short many- 
jointed antennee. The larvae and pupae resemble the neu- 
ters ; the latter are wingless. This suborder is represent- 
ed by the family Termitidce alone. 
isopterous (I-sop'te-rus), a. [< NL. isopterns 
(cf. Gr. iaoTTTepof, poet., swift as flight), < Gr. 
tffoc, equal, + irrepov, wing.] Having the wings 
equal ; specifically, pertaining to the Isoptera or 
white ants, or having their characters. 
isopurpuric (i"so-per-pu'rik), a. [< Gr. loaf, 
equal, + L. purpureus, purple : see purple.] 
Same as purpuric isopurpuric add, C 8 H B N 6 6 , 
an acid not known in the free state, but forming a potas- 
sium salt when strong solutions of picric acid and potas- 
sium cyanide are mixed. It was formerly used as a dye, 
under the name of grenat soluble. 
isopurpurin (i-so-per'pu-rin), n. [< isopiirpur- 
(ic) + -iiP.] A coal-tar color (Ci4H 5 O 2 (OH) 3 ) 
used in dyeing, closely allied to alizarin, formed 
by heating beta-anthraquinon disulphonic acid 
with caustic soda and potassium chlorate. It is 
sold in commerce under the name of alizarin, and pro- 
duces the yellow shade of red, while true alizarin gives 
bluish shades of red. Also called anthrapurpurin. 
Isopyreae (I-so-pI're-e), . pi. [NL. (Eeichen- 
bach, 1837), < Isopyrum + -ea>.] A former tribe 
of plants of the natural order Ranunculacea;, 
typified by the genus Isopyrum : now merged 
in the tribe Hellebores. 
Isopyrum (i-so-pi'rum), n. [NL. (Linnaeus), 
< L. isopyrmn, < Gr. Ic6vvpov , a plant not iden- 
tified (Fitmaria capreolata%),<. laof, equal, + vrv- 
poc, wheat (or irvp = E. fire).] A small genus 
of plants of the order Sanuneulacew, the type of 
the old tribe Isopyrew. They are slender smooth 
herbs with perennial root, bi- to triternately compound 
leaves, and solitary or loosely panicled white flowers. 
Seventy-five species are known in the north temperate 
portions of both hemispheres. 
isorrhythmic (i-so-rith'mik), a. [< Gr. to-of, 
equal, + pvff/ioc, rhythm : see rhythm.] In awe. 
pros. , having the same number of morse or units 
of time in thesis and arsis: as, an isorrhythmic 
measure or foot; characterized by such pro- 
portion (1:1) of thesis and arsis: as, the isor- 
rhythmic class of feet ; isorrhythmic movement. 
The isorrhythmic class (of feet) consists of the 
tetrasemic feet, namely : the dactyl ( | >- ^), 
the anapest (~ -- \ ), and the spondee ( | ). 
isosceles (I-sos'e-lez), a. [< L. isosceles, < Gr. 
roomefAfa, with equal legs (iaoCT/cE?.f rpiyuvov, a 
triangle with two sides equal), < ioof, 
equal, + ovce/lof, leg.] Having two 
legs or sides equal: as, an isosceles 
triangle. 
Isosceles (I-sos'e-lez), n. [NL. : see 
isosceles, a.] A genus of cerambycid isosceles 
longicorn beetles. Newman, 1842. 
isoseismal (i-so-sis'mal), n. and a. [< Gr. ;<rof, 
equal, + aia/i6f, a shaking, an earthquake: 
see seismic.] I. n. A curve or line connecting 
points at which an earthquake-shock is felt with 
equal intensity, or at which there is an "equal 
overthrow" (Mallet). See homoseismal. 
II. a. Belonging or related to an isoseismal; 
having the character of an isoseismal : as, an 
isoseismal curve. 
isoseismic (i-so-sis'mik), a. Same as isoseis- 
mal. 
