pyramid 
sides, which are necessarily all triangle?, having for their 
bases the sides of the base of the pyramid. Any pyramiil 
is In volume tine third of a prism that has the same bane 
and altitude. Pyramids are denominated from the figures of 
their bases, being triangular, square, pentagonal, etc.. ;ir. 
cordlng as the base la a triangle, a square, a pentagon, etc. 
Knowledges are as pyramid*, whereof history ii the 
basis. Bacon, Advancement of Learning, ii. 166. 
3. In eryatal., a form, in any system but the 
isometric, bounded by eight, twelve, sixteen, or 
twenty-four planes, and consisting of two four-, 
six-, eight-, or twelve-sided pyramids placed 
base to base. The name is also extended to embrace 
any form the planes of which intersect all three of the 
axes; in the monoclinlc system It Includes only four, and 
In the tricllnlc only two planes, being In each case an open 
form. If the planes Intersect the lateral axes at the as- 
sumed unit distances, the pyramid is called a "nit pyra- 
mid ; other forms are designated macnrpyramidn, clinupyr- 
ainids, etc. (see these terms), according to their position. 
In the tetragonal system a unit pyramid is also called a 
protopyramid, or pyramid of the nrst order or series, and 
a square octahedron formed by pyramidal planes parallel 
to one of the lateral axes is In distinction called a dntlero- 
pyramid or diametral pyramid, or one of the second or- 
der or series. These terms are also used In an analogous 
manner in the hexagonal system. 
4. In zool. and aunt., a pyramidal or conical 
part, structure, or organ ; specifically, a mass of 
longitudinal fibers on each side of the anterior 
median fissure of the oblongata. See cut un- 
der Elasmobraitchii. 5. The pile of five or six 
triangular valves covering an opening on the 
oral surface of the body of a cystic criuoid. 
The structure is variously interpreted as ova- 
rian or oro-anal. 6. In medietal arch., a pin- 
nacle of quadrangular plan, most commonly 
Pyramids. Apsidal Buttresses of Rheims Cathedral, France. 
acutely pyramidal in form; hence, any similar 
feature. Compare pyramidion. 
Accordingly at Amiens this weight is set ... in the 
form of an upright square mass of masonry crowned by a 
steep pyramid, and the Gothic pinnacle stands forth in 
essential completeness. 
C. H. Moore, Gothic Architecture, p. 84. 
7. The American columbo, or Indian lettuce, 
l-'raxcra Carolinennix Decussation of the pyra- 
mids, the crossing over of the crossed pyramidal tract of 
one side to join the direct pyramidal tract of the other, 
revealed externally by bundles crossing the anterior me- 
dian fissure of the oblongata a little below the olivary 
bodies Double pyramid group, seej/roupi. Mal- 
pighian pyramids, see MalpigKia n. Posterior pyr- 
amid, a lunlonloi gracilis. (Rare.) Pyramid of the 
cerebellum, a lobe of the vermis inferior of the cerebel- 
lum, behind the uvula. It is connected laterally with the 
digastric lobes. - Pyramid of the thyroid gland an 
occasional conical third lobe of the thyroid gland. Pyr- 
amid Of the tympanum, a small conical bony prom- 
inence on the posterior wall of the tympanic cavity, be- 
hind the fenestra ovalis, containing the stapedius mus- 
cle in its interior, and transmitting the tendon of that 
muscle through a foramen at its apex. Pyramid Of 
the vestibule, a prominence on the inner wall of the 
vestihular cavity, behind the fovea hemispherica. Pyr- 
amid Of Wistar, the splienotnrbinal bone. Pyramid 
POOL See poof-', n., 2 (a). Pyramids of Ferrein, a 
name given to the bundles of straight renal tubules which 
constitute the medullary rays. These bundles as thr> 
approach the cortical iiiaririn become smaller ami inure 
conical from the diminution of the number "f tubules, 
whence the name. Pyramids of the medulla oblon- 
gata, anterior and pusterinr. See def. 4, and posterior 
pyramid, above. Pyramids of the spine, a namr uivt-n 
to the anteriorly projecting parts of the spinal column. 
4873 
The upper pyramitl Is formed by all the vertebra from the 
second cervical to the last lumbar, and this Is again aul> 
divided Into three lesser pyramids ; the loicer pyramid is 
composed of the sacrum and coccyx. 
pyramidal (pi-ram'i-dal), . [= F. pyramidal 
= Sp. piramidal = Pg. pyramidal = It. /iira- 
midale = D. piramiedaal, < ML. pyramidalix, 
pertaining to a pyramid, < L. pyramis (-mid-), a 
pyramid: see pyramid.} 1. Pertaining to a 
pyramid, or having its form. Also pyramidical. 
He [Plato] would compound the earth of cubical and 
Are of pyramidal atoms, and the like. 
Cvdirorth, Intellectual System, p. B?. 
These meadows are planted with mulberry trees, and 
adorned by the pyramidal tomb of Cains Cestius. 
JMl , Italy, I. xi. 
2. In hot., anat., and zool., shaped more or less 
like a pyramid ; conical; pyriform pyramidal 
bell-flower, an ornamental plant, Campanula pyramida- 
lit. Also called chimney-plant. Pyramidal bone, the 
cuneiform bone of the carpus; the pyramidale. Py- 
ramidal column. Same as fatcitulut <rrarHit. Tpy. 
ramidal hemihedrism. See hemihedrimn. Pynm- 
idal muscle, the pyramidalis. Pyramidal numbers, 
the third order of ngurate numbers. See figurate. Py- 
ramidal plane, in cryxtal. . one of the faces of a pyramidal 
crystal. See pyramid, 3. Pyramidal tract, a system of 
nerve-fibers which originate In the cortex, in the region of 
the central fissure, pass down In the posterior limb of the 
Internal capsule and the central section of the crusta, form 
the pyramids in the oblongata, and divide into the direct 
and crossed pyramidal tracts, to terminate in the imme- 
diate vicinity of and in close physiological connection with 
the origins of motor nerves In the anterior columns of the 
spinal cord. Some few fibers may pass to the lateral pyram- 
idal tract without crossing, and a few may cross and re- 
cross in the cord to the original side. (Also called pe- 
duncular tract.) The pyramidal tract crotsed la that part 
of the pyramidal libers which crosses in the oblongata to 
pass downward in the posterior part of the lateral column 
of the opposite side of the cord. The pyramidal tract di- 
rect is that part of the pyramidal fibers which descends 
the cord without crossing over to the contralateral side. 
It lies close to the anterior median fissure, and is some- 
times called the column aj Tiirct. 
pyramidale (pi-ram-i-da'le), H. ; \>\.pyramidalia 
(pir'a-mi-da'li-a). [NL., neut. of pyramidalis, 
q. v.] The cuneiform bone of the carpus, more 
fully called 0,1 pyramidale. 
pyramidalis (pi-ram-i-da'lis), n.; \>\.pyramida- 
les (-lez). [NL., sc. musculux, muscle: see py- 
ramidal.} One of several different pyramidal 
or pyriform muscles, (a) In human anat. : (1) The 
external rectus muscle of the abdomen, a small triangu- 
lar muscle, two or three inches long, arising from the oa 
pubis In front of the rectus, and inserted into the linea 
alba below the navel. More fully called pyramidalu ab- 
dmninis, and also recta* cxternut. It Is comparatively 
small and vestigial, and often absent, In man, represent- 
ing a large muscle which in some animals reaches from 
the pubes to the clavicles. (2) A slip from the occlplto- 
frontalis, Ij ing upon the nose, more fully called pyramida- 
lis nan. Also called dorsalu narium, procerus nan, and 
procerua. (6) In ornith., one of the two muscles of the 
nictitating membrane, situated upon the back of the eye- 
ball, of a pyramidal or pyriform shape, cooperating with 
the quadratus in movements of the third eyelid. See 
third cut under eyet. Pyramidalis abdominis. See 
def. (a) (1). Pyramidalis femoris. Same as mjrifnr- 
tnw. Pyramidalis narium. Same as levator tabu ru- 
periorix alafque nan (which see, under Uvatur). See also 
sneering-muscle, under mutdcl. Pyramidalis nasl See 
def. (o)(2). 
pyTamidalism(pi-ram'i-dal-izm), n. [<.j>yram- 
idal + -Utm.} The body of facts or beliefs re- 
specting the pyramids of Ghizeh. C. Pia;;i 
Smyth. 
pyramidalist (pi-ram'i-dal-ist), n. [< pyrami- 
dal + -i.vf.] A pyramidist. 
pyramidally (pi-ram'i-dal-i), adr. In the form 
of a pyramid: as, a part pyramidally produced; 
in a loose sense, so as to form a high, angular 
elevation ; hence, extremely. 
If, according unto his (Aristotle's] own ethlcks, sense Is 
not essential unto felicity, but a man may be happy with- 
out the apprehension thereof, surely in that sense he is 
pyramidally happy. Sir T. Broumc, Vulg. Err., vll. 13. 
pyramidate (pi-ram'i-dat), a. [< pyramid + 
-ate 1 .} In entom., pyramidal; jutting out into 
a prominent angle : as, a pyrami- 
date fascia. 
Pyramidella (pir'a-mi-del'a), . 
pfL. (Lamarck, 1796), dim. of L. 
pyramis (-mid-), a pyramid: see 
pyramid.} The typical genus of 
Pura m ideUidse. 
Pyramidellacea (pir-a-mid-e-la'- 
se-a), . pi. [NL., < Pyramidella + 
Same as Pyramidellida. 
i^,,mt,iia 
Pyramidellidse(pir v a-mi-deri-de), <;''> * 
n. ]'l. [XL., < Pyramidella + -idee.] 
A family of gymnoglossate holostomatons pec- 
tinibraurhiate gastropods, typified by the ge- 
nus Pi/r<iinid<-lla. The animal has flattened auriform 
tentacles, eyes sessile on the tentacles In-hind, a long re- 
tractile proboscis, and a im-utum below tin- mouth. The 
shell is tuneted or conic, with the nucleus sinistral and 
the rest of the shell dextral, aperture entire, and culmnvl- 
pyrena 
lar Up plicated or simple. Species are distributed In all 
temperate and warm seas. 
pyramides, . Plural of pyramit. 
pyramidia, . Plural of pyramidion. 
pyramidic (pir-a-mid'ik), a. [< pyramid + -c.] 
Having the form of a pyramid ; pyramidal. 
Their gold in pi/ramidie plenty piled. 
Shenttime, Elegies, xlx. 
pyramidical (pir-a-mid'i-kal), a. [< pyramidif 
+ -/.] Same as pyramidic. 
The contrivance of nature Is singular in the opening and 
shutting of blndeweeda, performed by five Inflcxures, dls 
tlngulshable by pyrainidinil figures, and also different 
colours. Sir T. Browne, Garden of Cyrus, III. 
This bounding line (of a building] from top to bottom 
may either be inclined Inwards, ana the mass therefore 
pyramidical ; or vertical, and the mass form one grand 
cliff ; or Inclined outwards, as In the advancing fronts of 
old houses. Jtwtlcin, Seven Lamps of Architecture, ill. f 6. 
pyramidically (pir-a-mid'i-kal-i), adr. In a 
pyramidical manner; in the form of a pyramid. 
Pellon, being the least, Is placed above Oua, and thus 
they rise pyramidieally. J'ope, Udyssey, xi. , note. 
pyramidicalne88(pir-a-mid'i-kal-nes), n. The 
character of being pyramidic. Bailey, 1727. 
pyramidion (pir-a-rnid'i-on), n.; pi. pyramidia 
(-8). f NL., < Gr. 'irvpauioiov, dim. of mipa/iif, a 
pyramid: see pyramid.} In arch., the apex in 
the shape of a small pyramid which often ter- 
minates the top of an obelisk, and was very 
commonly sheathed with a cap of metal : often 
applied to any comparatively small structure 
or member of pyramidal shape. 
pyramidist (pir'a-mid-ist), . [< pyramid + 
-/<.] One wno makes a special study of the 
pyramids of Egypt, or is versed in their struc- 
ture and history. 
pyramidoid (pi-ram'i-doid), n. [< Gr. irvpa- 
/jif(-/ui-), pyramid, + riMof, form. Of. pyra- 
moid.] A parabolic spindle. Also pyramoid. 
Bailey. 1727. 
pyramidoidal (t)ir-a-mi-doid'al), a. [<pyrami- 
doid + -<i/.] Having the shape of a pyrami- 
doid. 
pyramidon (pi-ram'i-don), H. [< pyramid + 
-on, as in harmonicon, accordion, etc.] In or- 
gan-building, a stop having wooden pipes in 
the form of an inverted pyramid, about four 
times as large at the top as below, and giving 
very deep tones somewhat like those of a 
stopped diapason. 
pyramid-shell (pir'a-mid-shel), n. Any mem- 
ber of the Pyramidellidx. 
pyramis (pir'a-mis), n.; pi. pyramides (pi-ram'- 
i-dez). [L., a ^pyramid: see pyramid.] A pyr- 
amid. Formerly also piramix. 
Make 
My country's high pyramidei my gibbet, 
And hang me up In chains! 
Shall., A. and C., T. 2. 61. 
Place me, some god, upon a pyramu 
Higher than hills of earth, and lend a voice 
Loud as your thunder to me. 
Beau, and Fl., Phllaster, IT. 4. 
At the end of this Labyrinth there stood a square / V" 
muof a marvellous breadth and answerable altitude. 
Sandy*, Travailes, p. 88. 
Pyramis vestlbull, the pyramidal eminence of the ves- 
tibule. 
pyramoid (pir'a-moid), n. [< Gr. m'pa/ioeiSiff, 
Jike a pyramid, < m>pa/uf (-fuA-), a pyramid, 4- 
rliof, form.] Same as pi/ramidoid. 
pyramoidal (pir-a-moi dal), a. [< pyramoid + 
-<>/.] Same as pyramidoidal. 
Pyranga, . See Piranga. Vieillot, 1816. 
pyrargyrite (pi-rar'ji-rit), n. [< Gr. *vp, fire, 
+ apyvpof, silver, + -ite"*.~\ An important ore 
of silver, consisting of the sulphid of silver and 
antimony. It occurs in crystals belonging to the 
rhombohedral system, often highly complex, and also In 
massive forms. When transparent It has a deep ruby-red 
color by transmitted light, though on the surface It Is 
nearly black with a metallic adamantine luster ; the streak 
has a cochineal-red color. Also called nifty nicer, or, in 
distinction from proustite, dark-red nirer ore. The com- 
mon Spanish name in Mexico and South America Is ronder 
otcuro, or sometimes petlanque. See prouttite. 
pyratet, . and P. An obsolete spelling of pirn te. 
pyre (Pr). [= 8p. pira = Pg. pyra = It. pira 
(ct. F. pyrfe), < L. pyra, < Gr. irvpa, Ionic Kt'pfi. 
a heartn, the place of a funeral fire, a funeral 
pile, a monnd raised on the place of a pyre, < -i/i 
= E. fire: see Jtrc.] A pile or heap of wood or 
other combustible materials for burning a dead 
body; a funeral pile. 
For nine long nights, through all the dusk)' air, 
The pyret thick flaming shot a dismal glare. 
Pope, Iliad, I. 72. (Kichardim.) 
Apollo's upward fire 
Made every eastern cloud a silvery pyre 
Of brightness. Keatt, Endymiot'. i. 
pyrena (pi-re'nji). .; pi. pyreiiee (-ne). [M..: 
see yffWM 1 .] Same as pyrene 1 . 
