Andrew Pritchard.

A history of Infusoria, including the Desmidiaceæ and Diatomaceæ. British and foreign online

. (page 135 of 158)
Online LibraryAndrew PritchardA history of Infusoria, including the Desmidiaceæ and Diatomaceæ. British and foreign → online text (page 135 of 158)
Font size
QR-code for this ebook


broad, with horizontal pimctated lines
on each side of the median suture, and
denticulated junction-margins ; disc with
a series of marginal pimcta. s GaUumeUa
granulata, EA. p. 123; M. many figures ;
G, tenerrima, EM. pi. 39. f. 60; OrthO'
sira punctata, SBD. ii. p. 62, pi. 58. f.
839. Fresh water. Ehrenberg gives
upwards of 50 habitats in Europe, Asia,
and America.

M. ^. maxima. Disc with 81 mar-
ginal denticulations; and strongly a^
to M. sulcata,

M. Mdrchtca (E.). — Resembles M,
grantdata ; but the dotted lines are pa-
rallel io the suture, and not horizontal, s
QaUUmeUaMarcMca^'EM., several figures;
O, procera, EM. pi. 15 a. t 1. fVesh
water. Europe, Awa, Africa, and Ame-
rica.

M. decussata (E.). — Resembles M,
granulata ; but the dotted lines aie dia-
gonal and decussatnig. a OaUionetta de-
cussata, EM. several figures. Fresh
water. Asia, Africa, and America.
Kiitzing includes, perhaps correctly, M.
Marchica and M. granulata under this
species.

M. lirata (E., K.).— Has the habit of
M. granulata, but with more conspi-
cuous lines, disposed like the strings of



; a lyre. KBA, ^ SL=: GaOumeOa lu^MtOj
I EM. pL 2. 3. f. 33. Fossil. America.
I M. spiraUs (E., K.). — Filaments curved
, and sniral ; joints small, oblique, longer
than oroad, or ^ual, looaely ponetated
' in transverse series. KSA.p,3L = GW-
UoneUa spiralis, EM. pL S3. 13. L 3.
FossiL Oregon. Diam. 1-2804".
' M. Americana (Kiita.). — ^Frustules in-
; duded in a jointed cylindrical tube,
separated by dissepiments of the tube,
I ellintic, wiui striated margins and a
median furrow; disc wit£ ladiatiiig
striae, convex. KB. pL 80. £ 6a = CMb-
sira Americana. Diam. 1-600". Appa-
rently frimished with internal ailictoits
cells.

M. DickieU (Thwaites, K.).— JointB
mostly longer than broad, smooth or ob-
scurely punctated, except by ccmapicnood
dots boitiering the suture ; disc obecurd j
punctate ; sporangia ? fusifonn. KSA.
p. &d^,^Orthosira Diekien, Thwaites,
ANH. 2nd series, i. pL 12; SBD. ii.
p. 60, pi 52. f. 335. TKsh. water. Ckve
near Aberdeen, (xv. 29.) <' The fila-
ments of this beautifril q»ec]6B ooosist
generally each of frxmi two to foar frus-
tules, which are hyaline and perfectly
smooth ; central cavity fiilled with dark
red-brown endochrome ; sporangium
fusiform, marked with numerous annular
constrictions, whose formation is fno-
gressive, and which ^ on increaoii^
imtil the sporangiimi is fully developed
(xv. 296. 29 b. a filament, the tenninal
cells of which have each commenced to
develope a sporangium; and £ 29c. &
mature sporangium). This formalioD
thus occurs: at the commenoemoit of
the formation of a sporangium, the endo-
chrome, at the same time that it with-
draws from the end of the fi-ustule, pio-
duces at its centre an additional ring of
cell-membrane ; and, this prooeaa con-
tinuing to take place at certun intexrals,
each new ring of cell-menibrane exceed-
ing in diameter those previously fbraiedy
produces at length the structure rqire-
sented in f . 29 c ; or it may be a more
correct explanation of the process to aaj
that an entire new ceU-memloane has
been developed by the youn^ eponuiffimn
at the time each new nng has been
formed, and that thus have originated
the several chambers into which i£e ends
of the sporangium are divided; fiad-
parous division subseauently takeenlaee,
and sporangial frustules are develofped
from each half, as shown in £ 29 1>.^
Professor Smith doubted whether the
frisiform bodies are sporangia, as ^ tliia



Digitized by VjOOQ IC



OF THS MKLOSntE^.



821



mode of deyelopment, in the formiition
of sporangia, stands alone and unsup-
ported— -a serious difficulty in the way
<rf admitting Mr. Thwaites's conclu-
sions." For this and other reasons, he
was disposed to refer the process to the
develo^ent of internal cells, as in Meri-
dion, Himantidium, Odontidium, and
Achnanthes, and recorded his impression
that the process was not connected with
the sporangia.

AL tenuis (K.).— Very slender; joints

Srlindrical, smooth, longer than broad,
oseljr connected, produced at their
junction. KB. p. 54, pi. 2. f 2. In the
polishing powder of Lunebenr. Diam.

i-67eov

M. Garganica (Rab.).— Very slender ;
joints two or three times as lon^ as
raoad, with stou^ protuberant, mdi-
stinctly dentate jimctions; disc flat,

functated on the periphery. Rab D. p.
4, t. 2. f. a Italy. After burning, it
reminds one of M, tenuis.

Doubtful and imperfectly described
Secies,

M. Doayana (Van den BoschY — Joints
cylindrical, finely pnnctatea; length
equal to or a fittle longer than the
breadth. KSA. p. 29. Stagnant water.
HoUancL Diam. 1-1162" to 1-770".

M. cireularis, ^ OalHonella circularis,
EM. pL 85 A. 9. f. 3. Asia and America.
Filaments slender, curved ; jomts broader
than long, closely connected, smooth,
with a single sutimd line.

M. Oamca.^OaUianella Gallica, £M.
pL 9. 2. f. 2. Fossil. France. The
nrustule has one diameter twice as long
as the other, and no suture or striae.

M. hdUmkHa = OaUioneUa hahphUa,
EM, pL 37. 5. f. 1. Europe. Prustules
minute, smooth.

M. teaniatass GaUioneUa 'taniattif EM.
A, 39. 3. f. 66. Atmospheric dust. The
hguie shows a single subquadrate frns-
tide, without any distinguishing chur
lacter.

M. trachcali8= GaUioneUa tracheaUs,
EM. pi. 8. 2. f. 18. Hungary. Ehren-
berfi^s figure is too imperfect to be in-
teUigible.

M. laminaris = GaUioneUa laminariSf
EM. nl. 39. 3. 1 64. Asia. The imper-
fect ^ure shows striated junction-mar-
gins.

M. Scala ^ GaUioneUa Scala, EM. pi.
a 1. f. 24 Hungary. The figure ro-

S resents a slender continuous nlanient,
ivided into smooth quadrate joints.
M. ? mesodon = GaUionelia Y mesodon



t



(FragUaria mesodon?), EM. pi. 11. f. 16.
Bohemia. Filament slencler, conti-
nuous, with smooth subquadrate joints,
haying two puncta at each outer margin,
as in FragUaria.

M. ochracea,^ GaUioneUa ferruginea
(Ralfe). — Slender, oval, convex at both
ends ; smooth. In many, perhaps in all
chalybeate waters, and also in peat-
water, which contains a small proportion
of iron, this is to be found ; it is of the
colour of iron-rust, and in mineral
springs, in which it abounds, is often
taken for precipitated oxide of iron. It
covers evervtning under water, but
forms so deucate and fioccose a mass^
that the least motion dissipates it. In
the n>ring of the year, this mass is com-
posed of very delicate pale-yellow glo-
Dules, which can be easily separated
from each other. They unite together
in rows, like short chams, and produce
an irregular gelatinous felt or fioccose
substance. About summer, or in autumn,
they become developed into more evi^
dently articulated and stiff threads, of a
somewhat larffer diameter, but still form
a complicated mass or web, and, either
from adhering to each other or to deli-
cate Confervce, appear branched ; in the
young condition, when examined under
shallow ma^fiers, they resemble gda-
tine ; but with a power of 300 diameters,
the fiexible granules are discoveraUe,
and, with dexterous management, the
littie chains forming the felt or fioccose
web can be made out. In summer, on
the other hand, its structure can be ob-
served much more easily and distinctiy.
Eariy in spring, the colour is that of a
pale yellow ochre ; but in summer, tiiat
of an intense rusty red. Diam. 1-1200".

According to Kiitzing, this is not a
species of GaUioneUa, but a Conferva ;
it has no true sUicious lorica, as have
true Diatomea) ; and the coating of oxide
of iron is not an essential element, but
merely an incrustation, such as wiU form
on weU-known Confervae placed under
like circumstances, i. ^. in water holding
salts of iron in solution, which are suIh
sequentiy precipitated by exposure to
the air, and converted into the red oxide.

The same author differs from Ehren-
beig as to the part placed by the so-
called GaUiotieUa femtgtnea in the pro-
duction of the oxide of iron in chalybeate
waters, of bog-iron ore, of clay-iron ochre,
&c. For, he observes, in many springs
rich in iron no such organism is found,
although other Confervte may be present
— Confervfo, however, not peciuiar to



Digitized by VjOOQ IC



822



8Y8TE1IATIC HISTORY OF THE IXFU80BIA.



Boch habitats, but common in springe
and ponds generall^r.

Mr. Ral£ (op, eU. p. 862), however;
in part supports Ehrenberff, declaring
that, thougn identical witk Conferva
^diraeea (Dillwyn), yet ^< Ehrenberg is
no doubt correct in placing the plant in
^iis genus, as tlie fituonents are silicious
and cylin(hricaL*'

Nageli describes and figures a species
which he refers to the genus Ghdlionella \
but it is a doubtful member. His de-
scription, however, espedall]^ that of the
self-division, induces us to give it nearly
in his own words, with his name (Ray
Society, 1846, p. 219).

M. NdgeU (R.).— Shortly cylindrical;
diam. -014 ' to W\ Manne. Naj^

''Both the terminal sur&ces oi the
c^ Under are flattened ; so that, when seen
sideways, it appears rectangular, with
the angles rounaed off. It is composed
of one simple ceU, whose membrane is
covered by a siliceous plate; and its
cavitv contains chloitiphyll-granules,
whicn lie upon the membrane in two
circular bands, (xv. 26-2a) Each of
these bands occupies one of the obtuse
angles of the cylinder^ and appears annu-
lar from above, rectibnear firom the side.

'' In developing, the relative len^fth of
the cylinder increasing, a septum divides



it into halves (xv.



which when
complete^ the latter separate as two di-
stinct beings. The nascent chlorophyll-
granules are either spread equally over
Uie surface, or more frequently arranged
in radii from the nucleus in tne cenfie ;
they lie in the course of the currents
streaming from the nucleus. Compared
with a cell of Conferva, or of Spirogyra,
all three agree in the forming of a septum,



in the similarity of their ccmtents, and in
the depositions of extra-cellular sub-
stance. But Gallionella differs from
both, by the production of an individual
from every cell, also by the chlorophirll
forming two lat^al bands, and the sui-
ceous extra-cellular substance an inter-
mediate one.

''So fiur as my inveatigatioiis go,
Gallionella, which, according to Ehren-
berg, possesses a biyalved or multivalved
shield!, agrees with the above-deecribed
plant in all essential particulars. The
lines, for instance, which would intimate
a division of the shell into two or more

Sieces, are the septa by which the cdl-
ivision is effectc^L As in the fiHifima
AlgSB^ these walls at first appear as deli-
cate Imes ; then, by an increase of thick-
ness, seem two clearly defined lines ; and
at last present themselves as two lamVllg,
separated by an intermediate third line.
Tne perforations which Ehrenbeirg de-
scribed, I look upon as nothing more
than intercellular spaces, formed be-
tween the two new-&rmed cells and &e
parent cell. These so-called pefforatioos
are only visible, therefore, on the two
lateral borders where the wall abuts
upon the membrane. The Confervotd
AlgBd exhibit a similar appearance.''

OaHioneUa (?) Not49 HoUandut (^X
Avon River, Australia ; Q* gMa V^-U
fossil, Geoivia; (?. puntiaUi (Ehr.l
Western Am; Q, tmcta (Ehr.), Ural
Mountains; Q^gemmaUiC^bi.\BSiheDh\
G. ftit«oJ0to(Ehr.), fossil, North Asia
0» untUAa (Ehr.), Himalaya Mountains
6?. cunxtta (Ehr.), India; O. rmPMrfa
(Ehr.), India; G.IfMiea(EhT.),Bmt
Nile, are species known to us only by
name.



Genus ARTHRGGYRA (Ehr.). — ^The characters of this genus are nnknowB
to OS ; but, judging frrom iSirenberg's figures of the species, it seems to have
been constituted for the reception of those fonns of Melosira which, like Jf.
Dickieii, produce horizontal, elongated, taperipg internal bodies or sporangia.



Abthbootra OtiatimalensiSf EM. pi.
83. 6. f. 1. Fern-earth. Guatemala.—
Filament straight^ jointed, with crenated
margin, and straight, fiuoform internal
body.



A. semOtmaris, EM. pi. 38. a £ 2.
Guatemala: — ^Filament jointed, curved,
with crenate marginsi and semilunate
internal body.



Genus DI8C0SIRA (Rab.).— Frustules united into a short filamait, with
a thick mucous covering ; in lateral view circular, having a unifoimly punc-
tate centre, a border of numerous (24 to 38) slightly curved, obUque, rar-
like lines, and a marginal crown of teeth (50 to 64).

DiscosiRA sulcata (Rab.).— Frustules I rows, which conespond to the teeth of
m front view with deep transrerse fur- | the lateral surface. KabD.p. 12, t, 3. In

Digitized by VjOOQ IC



OF TUX HEL0S1BX^«



a kgoon at Manfredonia, east coast of
Italy. Each tooth is minutely denticu-



late, but requires the highest mag
ing powers to ascertain it. (v. 68.j



Genus LIPAROGYRA (Ehr.). — Frustules simple, cylindrical, each having
an internal spiral filiform band or crest.

The habit of this genus closely resembles that of Spirogyra, a non-silicious
genus of Algse.



LiPABOOTRA dendroteres (R). —
Frustules smooth, crystalline, three or
four times as long as broad, with an
internal spiral band; maigin of disc
denticulated Rah D. p. 12. =Z. gpiraUs,
EM. pL 34. 6a. f. 1, 8. On trunks of
trees. Venezuela. Thirteen spirals in
l-36(r. fv. 72.^

L. circularU uL). — ^Frustule with 13
annular turns of internal line in I-36(X'.



Rab. /. c, p. 13. With the preceding, and
in Brazil. fSirenberg says he is not
satisfied whether the |Mreceding are di-
stinct species, or merely varieties. Each
has a smootn disc, with three central
apiculi.

L. aeaktrisy EM. pL 34 5a. f. 2. South
America. Ehrenberg's figure represents
the firustule in front view as divided by
cross bars in a ladder-like manner.



Genus POROCYCLIA(Ehr.). — Resembles liparogyra, but is without spires,
has interior circular rings, and the margin of its disc-like ends a circlet of
deep impressions. We doubt whether this genus is sufficiently distinct from
Liparogyra.

PoBOCYCLiA dendrophila (K^. — I radiating series of puncta, and 5 central
FroBtules smooth, with 9 annular lines ; I ^iculi. Rab D. p. 12. On trunks of
disc with 12 marginal depressions, I trees. Venezuela. L. 1-32(X' ; w. 1-560".

Genus STEPHANOSIRA (E.).— Frustules united into a short filament ;
disk with radiating series of minute puncta, and a marginal crown of teeth.
In form this genus resembles Stephanodiscus, but differs from it, and becomes
allied to Melosira by its imperfect spontaneous division, and consequent con-
catenation. In Melosira, however, the circlet of spines is wanting. We are
unacquainted with this genus ; and its characters scarcely sufSce to distinguish
it from Orthosira. All the known species are found on trees.

preceding species. Diameter 1-720".

S. Buroptea (E.). — Frustules often
broader than long, snM>oth, but with very
fiuntly striated junction-margins. Rab.
/. c p. 14. Among mosses on trees at
Berlm. Much smaller than the preced-
ing. Chain formed of three to four frus-
tules, each 1-2304" to 1-1162" in depth ;
rarely 1-1200^' m width.



STBPHANOsmA EpidendroH (E.). —
Front view with punctated tnmsverse
lines and furrow. Rab D. p. 14. On trees.
Venezuela and B^raziL Larger diameter
1-432"; smaller 1-4320^.

S. Hamadryaa ^). — In front view
smooth, but with junction-margins stri-
ated; disc having marginal radiating
Snncta, and its centre a few scattered
ots. Kab. l c, p. 14 On trees with the



Genus STEPHANODISCUS (E.).— Disc with radiating series of puncti-
form granules, and frimished with a crown of erect mar^al teoth. Aquatic.
Stephanodisci approximate in character to Cyclotella, but differ from them
by the cirelet of teeth. They also approach closely to the non-cellulose
Goscinodisceee, and seem to have as good a claim to rank with that family as
with the MelosiresD. Stephanodiscus differs frx>m Odontodiscus in the same
manner as Peristephaoia does from Systephania, and in our opinion might,
without inconvenience, be united to it.

Stbphanodiscus Berolinensis (EX teoth (often 32) on each side. KSA.
Smidl. discoid: disc nlano. find v radi- p. 21. Alive, Berlin. Diam. 1-1152'. In-
ternal granular substance brown, lobed.



—Small, discoid; disc piano, finely radi-
ated, and funushed with acute marginal



Digitized by VjOOQ IC



824



8Y8TEKATIC HISTOBT OF THE IKFTSORIA.



S. JS^mjnfiacus, EM. pL 33. 1. f. 16.
Egypt. Ehrenberg^s figure represents
the* disc with series of puncta radiating
from the centre, without a distinct um-
bilicus, the teeth nimierous, subulate,
and erect (v. 69.)

S. Sinensis, EM. pi. 34 7. f. 7. Canton.
Ehrenberg*8 iigure shows the puncta
arranged as in S. .^ypHacWj but the rim
striated, and the teeth nodide-like and
intra-marginaL

S. Bramapuira, EM. pi. 35 a. fl 9, 10.



Gan^pes. Puncta as in the foregoing
species, the rim furnished with short
triangidar teeth.

S. NiagartB (R). — Fmstules small;
disc with numerous (often 64) series of
punctiform granules radiating from a
large granulated umbilicus, and as many
acute marginal teeth as rays. ISm.
pL 36 A. 7. f. 21, 22. Niagara. This
species is distinguished by its granulated
umbilicus.



Genus PERISTEPHANIA (Ehr.).— Frustiiles simple, discoid; disc with
decussating parallel series of granules, and numerous marginal teeth. Mari-
time. " The characters of this genus so well agree with Stephanodiseus thai
perhaps we might more correctly refer the deep-sea form to that genus. But
as the hitherto known Stephanodisci are all fluviatile, and the maritime fonn
in the order of its cellules very nearly approaches the purely maritime Ctmd"
nodiscus lineatus, I have preferred not mixing fluviatile Stephanodisci with
a doubtful maritime form. Perhaps the flow in deep water may have com-
mingled a fluviatile form with the maritime ones. Should, therefore, a similar
form be hereafter found in any river, this generic name must be cancelled, and
the form placed in Stephanodiscus " (EllBA. 1854, p. 236). As we consider
habitat altogether inadmissible as a generic distinction, we would distinguiah
Btephanodiscus and Peristephania by the radiating granules of the former,
and their parallel arrangement in the latter genus. We should prefer to
unite this genus wiih Systephania, which differs only in having intra- mar-
ginal teeth. Perhaps even Cosdnodiscus Vineattis might be included, thus
making the parallel arrangement of the granules the essential charaeter.



Pemstkphania Eutt/cha (E.). -—
Habit of Coscitwdiscus hneatus', margin
of the disc armed with numerous erect,
crowded teeth. EM. pL 36 B. 4. f. 14.
Deep soundings of the Atlantic (v. 73^

P. lineata (E.). — Resembles P,



Eiiiychay but its teeth are fewer and more
distant. EM. pL 33. 13. f. 22. Cahibmitfi
deposit and guano.

In both species the teeth are minute
and triangular.



Genus PYXIDICULA (Ehr.). — Fmstules simple or binately oonj<Hnod,
free or adnato, bivalved; central* portion obsolete; valves very convex. In
Pyxidicula the frustule forms a bivalved box, and differs fitnn C^dotdla in its
vaulted valves and the absence of an interstitial portion. The same charact^s
distinguish it from all the Coscinodisce©. As first constituted by Ehrenberg,
Pyxiicula contained very heterogeneous forms ; by the formation, however,
of Mastogonia, Stophanogonia, gtephanopyxis, and Xanthiopyxis as distinct
genera, this defect has been in a great measure removed ; but we believe it
still includes some doubtful species. Dictyopyxis was separated bj Ehrrai-
berg, first as a subgenus and afterwards as a genus, for those forms character-
ized by the cellidose structure of the valves, leaving in the original genus the
sinooth and punctated species. We have thought it more desirable to repaid
Dictyopyxis as a subgenus only, xmtil some of the species are more fully
known.



♦ FrushUes smooth or minutely punctate.
Pyxidicula.

Pyxidicula operculnta (E.). — Fms-
tules small, orbicular, hyaline, punctated.



EM. pL 16. 1. f. 46. = P. mifwr, ESA.
p. 21. Fossil, Sweden ; recent, Ajsia. Eng-
land P l)iam. 1-1440" to l-67(y'. Valvea
joined by a distinct suture. Kiitsinfr
refers P, operndata (E.) to Cyclotella.



Digitized by VjOOQ IC



OP THE MELOfilBXJE.



826



p. Adriatiea (Kiitz.). — ^Adnate, sessile,
of middle size; valves convex, nearly
hemispherical, very smooth. KB. t 21.
f. a Adriatic, (xui. 33.) Diam. 1-600".

P. ? prceUxta (E.). — Valves geminate,
sliebtly hispid, neither cellulose nor
radiated, but bordered by a raised limb ;
middle Hat KSA. p. 22. Fossil. Greece.
Diam. 1-1152".

P. f* urceoktris (E.). — Valves geminate,
unequal, urceolate (the one more convex,
elongated; the other shorter), each with
a plane, raised limb ; cellules none, but
about ten smooth rays in the longer, and
eight apiculate ones in the shorter valve.
= Dictyopyxis ureeolaris, EM. pi. 18. f. 3.
Fo6siL Virginia. Diam. 1-1/28".

P. loHffa (R). — Oblong, two and a
half times as long as broad, cylindrical,
with rounded en(£ ; suture longitudinal.
KSA. p. 22. Fossil. Virginia. L. 1-1080".

2* Fnulules cellulose. Dictyopyxis (^.).

P. cruciata (E.). — Frustules oblong,
with rounded ends; cellules lar^, ar-
ranged in parallel lines; rim distinct
EM. pL 18. f. 2, = Coscinodiscus cruciatm,
KSA jp. 125.

fi, JEieUenicay smaller = Dictyopyxis ffel-
Imica, EM. pL 19. 1 13. FossiL America.
Guano, &c. Frequently the disk has
some series of its cellules more conspi-
cuous and forming a cross. Valves cam-
pan ulate.

P. CyHndrus (E.). — Cylindrical, with
rounded ends, three times as long as
broad ; valves with obscure rows of cel-
lale». EM. pi. 33. 13. f. 8. Fossil. Mary-
land. Diam. 1-OGO". Valves campauu-
late, separated by a suture.

P. Zens (E.).— Frustules laterally de-
pressed, lenticular, cellulose; valves in
m>nt view semielliptic EM. pi. 18. f. 5.
Fossil. Virgmia. Diam. 1-030". The
firuatule is oval in the front view, the
suture forming the greatest diameter.

P. areolaUi (E.). — Valves with a
heptagonal, areolate, punctated centre,
and seven lateral punctated areolae.
KSA. p. 22. North America. D. 1-900".

P. gcmmifera (E.). — Valves turgid,
crystfldline, not bordered, furnished with
lax senes of crystalline nodules, fifteen
of which very nearly reach the smooth
centre. KSA. p. 22. Fossil. Maryland.
Diam. 1-792".

P. campressa (Bail.). — Frustules'ellip-
tic, bivalve ; valves separated by a piano
passing through the longer axis, slightly
convex, and with transverse rows of dots.
BC. ii. p. 40, f. 13, 14. Florida.

P. dcnUUa (E.). — ^Frustules having the



convex margin furnished with (irregular)
slightly prominent little teeth ; cellules
, rather ^rge, in 1-1200". KSA p. 22.
t Antarctic Ocean. Diam. 1-840".
1 P. P limhata (E.). — Frustules oblonp,
with a central Keel ; valves showing m
; front a central cellular surface, and 32
! to 40 radiating lines; border not cel-
. lulose. as Stephanopyxis UnibatOj EM.
pi. 18. f 7. FossiL Maryland. D. 1-792".
Ehrenberg's figure is oval, and has a
broad^ distantly striated, but not cellu-
lose nm, and in its centre scattered gra-
nules.

P. cristata (E.). — Frustules with gemi-
nate, lenticular valves, which are close
together, not winged^ with a somewhat
prominent margin like a thin suture;
cellules of disc in roYr^,:= Stephanopyxis
cristata, EM. pi. 18. f. 0. Fossa Vir-
ginia. Diam. 1-810". Ehrenberg's figure
somewhat resembles that of P. limbata;
but the cellules of the oval valve are
crowded, and the striated rim is nar-
rower.

Obscure or doubtful Sjpecies,

P. NdgeUi (Kiitz.).— Smooth, one side
orbicular, girt with a membranous wing-
like ring ; the other side oval, one mar-
S'n more convex, umbonate in the mid-
e. KSA. p. 889. Switzerland.

P. Actinocyclus (E.). — Frustules with
two flattened, finely cellular and ele-
gantly radiated valves; rays 30 to 40,
straight and dense. EM. pi. 18. f. 19.
= CydoteUa Actinocyclus^ KSA. p. 20.
Fossil. America. Diam. 1-720". Enren-
berp figures only the lateral view, which
in its radiating series of dots resembles a
Coscinodiscus.

P. Scarabaus (E.). — Oblong, with
unequal valves ; when viewed laterally^
recalling the figure of the Scarabasus.
= Dictyopyxis 8carab€Bus, R Fossil.
Virginia. Diam. 1-648". Cellules 14 in
1-1150".

P. major (Kiitz.). — Frustules large,
elliptic, regularly punctated. KB. 1. 1.
f. 25. North America ; France. Diam.
1-420". Probably a state of P. cruciata.

P. glohata, — We insert under this
name certain spherical bodies of a dia-



Online LibraryAndrew PritchardA history of Infusoria, including the Desmidiaceæ and Diatomaceæ. British and foreign → online text (page 135 of 158)