Pleuroptera 
-I :,:,7 
A division of Hr<irlii<i/M>tlii, cuniMining the in- 
articulate or lyopomatous members of that 
clnss: contrasted with Aiiyijia : a&me &s Lyopo- 
mata. 
Dr. Horn exhibited seven ipecles of Pleocoma from 
( alifornla, of which three were new, and supported the 
views of the late Dr. L Conte of the position of this go- 
mis, which he Insisted was a Laparostict, and not a Pint 
rostict Lamelllcorn. Aaur. Xaturalut, XXII. 861 
' -"' ' Kcaritoxidx, including those forms which have 
the embryo with the radicle against one edge the abdominal spiracles (except the anterior 
of the cotyledons that is, with the cotyledons _**..-.- j -..*lv_ 
accumbent. Gray. 
plenrorrhea, pleuronrhoea (plo-ro-re's), n. stronglv, and with tl 
V S*"?^ th ? P leura > + ^"' Q ' a flow > usually' visible behi 
ilux.J Kffusion into the pleural cavity. The llgula is at ways conn 
Pleurosauridss (plo-ro-sa'ri-de), n. pi. [NL., 
- -idx.] A family of extinct 
ones) situated in the dorsal part of the abdom- 
inal segments, forming rows which diverge 
ith the last spiracle 4 
behind the elytra, 
ays connate with the" men- 
torn, and the lame have the lobes of the 
maxilla: connate. The other main division 
Ule ed with pleurothotonos. 
pleurothotonos (pls-ro-thot'o-nos), 
H. [NL., < Gr. ir)evp<i6ev, from the 
side (< jr>et>p<i, the side, + -Bev, from, 
an adverbial suffix), + r6i>of t ten- 
sion: see tone.] Tonic spasm in 
which the body is bent side wise: 
correlated with emprottkotonos and 
iiiiixthotonos. 
valves show, with a good micro- Pleurotoma(pl<j-rot'o-ma),n. [NL. 
eries of lines, capable, under high (Lamarck, 1801), < Gr. n-Xnyxi, the 
1 a favorable light, of resolution into * ide > + -/' ?. < Ttfoviv, Ta/telv, cut.] 
Imrefnvn fnTiiitiiitn<r -r/>oiir,t + In eoncli.. the tvuical trenus of I'll 
slit-like nares. Their remains have been fount! 
Klmmeridgian rocks of Bavaria. 
Pleurosaurus (plo-ro-sa'rus), n. [NL., < Gr. 
n'tevpt'rv, a rib, + aarpoc, lizard.] An extinct 
genus of lizard-like reptiles, typical of the 
family PlcuroxauriiUe. 
Pleurosigma (plo-ro-sig'mfi,), n. [NL., < Or. 
ir'/.evpa, the side, + aiypa, the letter 2, a.] A 
genus of Diatomaceee. containing species in 
which the ' 
scope, a series 
powers and a favorah.. ....., ...., .-,.,, , 
dots, and therefore furnishing excellent tests ln w'-. the typical genus of 1'lenratomiiln : 
for the power of a microscope. R . c *U e d from the notch or slit in the outer 
Pleurospondylia (plo'ro -spon - dil' i - :< ), . /. L|P.P* tlle aperture. Formerly the name was used for 
[NL.,< fir. r> rir xip,arib, + or!^,,, , a vertebra.] ^J^^lSS 'FEhfiXto " """ "**** '" 
One of the pn- Pleurotomaria (pl6'ro-t6-ma'ri-a), w. [NL. 
mary groups (Defrance, 1HU6), < (ir. ' 
into which 
Jtcj>tilia are di- 
visible. It is 
characterized by 
the immobility of 
the dorsal verte- 
Trans section of the Skek-l.jn i.f Llttlpiit 
miiias in the dorsal region, showing tlie dispo- 
sition of vertebra anil ribs, forming the cara- 
pace, and characteristic of rifHrosportrfylia. 
O, centrum of a vertebra ; /*, expanded neu- 
I >i ,r upon one an 
other, and of tho 
ribs upon these 
vertebra; (nnd by 
rarplatei/f.aribrCexpandedcostaTplatV; I' 1 " h ' ' 
M, marginal plate : P. a lateral element of transverse pro- 
the plastron. cesses from all the 
vertebra), this fix- 
Ity being secured by the union of superficial bony plates 
into which the ribs nnd vertebra; pass, forming a carapace, 
and further carried out by the development, in the ventral 
walls of the thorax and abdomen, of dermal lx>ncs, usually 
nine in number, of which one is median and asymmetrical, 
the others lateral and paired, the whole forming a plastron. 
The group contains the single order Chelonia or Testuili- 
nata, and is alone contrasted with Ilerptlrapiiiuli/lia, Pent- 
spomlt/lia, and SuchiatjKiiulylia collectively, which together 
include nil other Reptilia. See these words : also cuts 
under Chelonia, Chflonitlir, carapace, and ptatttron. 
pleurospondylian (plo'ro-spon-dil'i-an), a. and 
n. [< Pleuroxpondylid + -an.'] I. <i. Having 
the ri bs fixed immovably upon the vertebra? ; 
belonging to the PlturospondyJia, as a turtle or 
tortoise; chelonian; testudinate. 
II. n. A member of the Plturoxpondyliu, as a 
turtle or tortoise. 
a attfffrt 
from the Lias. 
the side, + ra/ni- 
fov, )irop. dim. of TO/UK;, a 
cut, slice, < ri/iveiv, Tauilv, 
cut.] The typical ge- 
nus of Plenroli>marii/l/F. 
Pleurotomariidae (plo- 
ro-tom-a-ri'i-de), w. pi. 
[NL., < Pteurotomaria + 
-idir.] A family of scuti- 
branchiate gastropods, 
typified by the geniiH 
I'letirotoiiiiiria. The animal has the muzzle simple; 
there is no frontal veil, the tentacles are simple, and 
the eyes on pedicels exterior to their bases; two nearly 
symmetrical gills are developed, 
and lateral fringes, lint no cirri, pro- 
ject from the sides; the shell Is 
troeblfonn, ami has a deep slit In 
the outer lip, leaving a fasclole on 
the completed whorls; the opercu- 
lum Is horny ami multlsplral or 
fmbspirnl. Four living species, in- 
habiting deep tropical seas, are 
known, and many extinct species, 
ranging from the Silurian epoch up- 
ward, as the Liassic Plnimtmnaria 
atvjlica. An ancient genus, ranging from the Devonian to 
the Trias, is Pnrcfltia, of which a typical species is P.piaori. 
pleurotomarioid (plo'ro-to-ma'ri-oid), a. and 
n. I, a. Of or relating to tne Plcurotomariidse. 
, . , II. w. A species of the family Plcurotoma- 
pleurosteal (pli>-ros'te-al), n. [< pleuroste-oi> r iida> 
+ , "'('-'I, La * eral and' costiferous, as a part pleurotomidse (plo-ro-tom'i-de), ti.pl [NT... 
of a bird's sternum; pertaining to the pleuros- < pt curo t oma + .,v te ;j A f am ii y o f toxoglos- 
teon. 
plenrosteon (pl^-ros'to-on), w.j pi. plenrogtea 
(-ii). [NL., < Gr. irZevpd, the side, + barton, a 
bone.] In ontitlt., the anterior lateral piece of 
the breast-bone ; that element of the sternum , 
which forms the costal process and with which Pleurotomme (plo-rot o-mm), L<Pleui 
ribs articulate : distinguished from lonhosteon, L, HH<> V ] Of or Kl&ted to shells of the 
family of toxoglos- 
sate gastropods, typified by the genus Pleiiro- 
toma. Most of them hare the shell spindle-shaped, with 
a prolonged canaliculate aperture notched near the suture. 
It contains about 500 species, sometimes known a 
shetts. See cuts under Lathrn* and Plrurntama. 
genus 
curtieoKteon, and metostcon. See cuts under 
enrinnte and i-jrijileura. 
Pleurosternidas (i>16-ro-ster'ni-de), w. pi. [NL.. 
< I'lrurostiTiiiini + -iWa>.] A family of pleuro- 
i turtles, represented by the genus Pleii- 
Pleurotoma. 
pleurotomoid (plQ-rot'o-moid), a. and n. [< 
Pleiirotoma + -otd."] I. a. Of or relating to the 
Pleurotomid-ie. 
H. . A shell of the familv . 
the entoplas 
The species lived during the Oolitic and Cretaceous pe- 
riods. 
Pleurosternum (plS-ro-ster'num), n. [NL., < 
Gr. T/fiyxiv, rib, -r rrripvov, the chest.] A ge- 
nus of extinct turtles, typical of the family 
Pleurtuitcrnidie. 
pleurosthotonos (plii-vos-thot'o-nos), . Same 
pleUTOStict (plo'ro-stikt), a. [< NL. i>l< iir<mti<'- 
tii*. < Cir. rr/nyiu, tlie side, + oriKTof, verbal adj. 
of artCetv, prick, stab: see stiyma.] In eiitmn.. 
lez). [NL., < Gr. 
a, the pleura, + NL. transversalis, q. v.] 
An anomalous muscular slip arising from the 
transverse process of the seventh cervical ver- 
tebra, and inserted into the top of the pleural 
sac. 
pleurotribe (plo'ro-trib), a. [< Gr. irtevpa, the 
side,' + rptptai, rub.] In hot., touching the 
side : said of certain zygomorphic flowers, es- 
pecially adapted for cross-fertilization by ex- 
ternal aid, in which the stamens and style's are 
so arranged or turned as to strike the visiting 
plemB 
insect on the side. Such flowersare especially adapt- 
ed to bees. 1'katenltu, Lalhyna tylveitru. and Pi<iuala 
tnyrlifdia are cxmple. Compare nalntribe and ittrno- 
tribe. 
pleurotropous (pl^-rot'ro-pus), a. [< Gr. vUt>- 
l>a, the side, + rpiintv, turn.] In oot., having 
the faces flat: noting the stems of certain spe- 
cies of Selaginella. Compare goniotropotu. 
pleurovisceral (pie-ro-vis'e-ral), o. [< Or. 
ir/fvpa, the side, + L. rincera, the internal or- 
gans : see risceral.] Pertaining to the side of 
the body and to viscera : specifically said of the 
connecting cord or loop between a'pleurol and 
a visceral nervous ganglion of an invertebrate, 
as a mollusk. Also rinreropleunil. 
plevint (plev'in), n. [Also pltrine, < ME. */- 
ine,<.OF.plevine,pterignc,pleurine,plrrene (ML. 
pletina, pleurina, pluHiui), a pledge, warrant, 
assurance, < plerir, pleirir, plenrir, pluvir, also 
plerer, pluver = Pr. plevir (ML. reflex plerire, 
jilirire), promise, engage, pledge, give in pledge, 
warrant, < L. prbere, proffer, offer, give (prse- 
bere Jidein, give a pledge): see prebend. Cf. 
pledge and replevin, repUry. ] In law, a warrant 
or an assurance. 
plex (pleks), r. . [<;>/jji.] To form a plexus. 
plexal (plek'sal), ti. [<plex-u + -/.] Of or 
pertaining to a plexus. 
plexed (plekst), a. [< L. plerus, plaited (see 
plexus), + -r<ft.~] Plaited, netted, or made 
plexifonn; plexiform. 
piexiform (plek'si-fdrm), a. [< L. plexus, a 
twining, plaiting (see plejrux), + forma, form.] 
1. In the form of network; complicated. 
Qnincy. 2. In anat., specifically, formed into 
a plexus, as nerves; plaited; plexed. 
pleximeter, piezometer (plek-sim'e-ter, plek- 
som'e-ter), H. [< Gr. f/'/fif, percussion (< JTA//O- 
etiv, strike: see plague), 4- /tfrpov, measure.] 
In iiu-d., an elongated plate, composed of ivory, 
india-rubber, or some similar substance, from 
14 to L' inches in length, placed in contact with 
the body, commonly on the chest or abdomen, 
and struck with the percussion-hammer, in di- 
agnosis of disease by mediate percussion. Also 
mesgineter, )ilfflotiieter. 
plezimetric (plek-si-met'rik), a. [< pleximeter 
+ -ir.] Of or pertaining to the pleximeter or 
its use. 
piezometer, . Bee plerimeter. 
plexor (plek'sor), >i. [NL., irreg. < Gr. vtijl-ic, 
percussion, < TT^OW iv, strike: see plague.] That 
which strikes in percussion ; a percussion-ham- 
mer. 
plexure (plek'gur), w. [< L. as if *pleivr<i 
(ML. f). (plectere, pp. plexus, interweave: see 
plerus.] An interweaving; a texture; that 
which is woven together. 
plexus (plek'sus), . [X L. plerufi, an inter- 
wea_ving, twining, plaiting, < plectere, pp. plex- 
us, interweave, twine, plait: see jj/ai'ry) 1. A 
network ; any collection of intimately coherent 
parts, as of an argument. 
Antecedent and consequent relations are therefore not 
merely linear, but constitute a plena; and this Btanu 
pervades nature. Amir. Jour. Sri., 3d ser., XXXI. 286. 
A perfect plexui of ideas that mutually support and In- 
terpret one another. Encyc. Brit., II. 6fi. 
2. In anat., an interlacing of nerves, vessels, or 
fibers; a net-like arrangement of parts, or the 
Brachial Plexus of Nerves in Man. 
V, VI, VII, I. II, the five main roots (anterior divisions of cervical 
and dorsal spinal nerves) of the plexus ; other cords and continuations 
of the plexus are named in the figure. 
parts so disposed: especially said of certain 
delicate vascular membranes chiefly composed 
