Diatomaceae of Philadelphia/Fragilarioideae

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Valve zygomorphous. Structure pinnate, not concentric. Valve divided either by a true raphe or cleft or by a linear space or line imitating a raphe.

Divided into three Groups:

1. Fragilarioideæ.—Valves without a raphe; usually with a pseudoraphe or median line.

2. Naviculoideæ.—Either one or both valves with a true raphe.

3. Surirelloideæ.—Valves in which the raphe is concealed near the margin on one or both sides of each valve in a more or less elevated keel or wing.


(a) Tabellarieæ.—Valve symmetrical with respect to both the longitudinal and transverse axes; septate, not cuneate.

(b) Meridioneæ.—Valve symmetrical with respect to the longitudinal axis, asymmetrical to the transverse axis, cuneate, finely striated.

(c) Fragilarieæ.—Valve of varied shape, not cuneate; costate or with transverse rows of puncta.


Frustule in zone view rectangular, in valve view linear or linear-elliptical, sometimes constricted in the middle, symmetrical to both axes, not cuneate; with two or more septa or annuli.

Chromatophores numerous, granular.

Rhabdonema.—Frustules with numerous septate partitions having one or several foramina. Transverse costæ or rows of coarse puncta.

Tabellaria.—Frustules with two to six nearly straight septa. Transverse striæ subtly punctate.

Grammatophora.—Frustules with two sinuate perforate curved septa. Transverse striæ subtly punctate.

Striatella.—Frustules with alternate partitions, septate or partly so.

Attheya.—Frustules not septate but with numerous annuli.

Rhabdonema Kuetz. (1844)

(rhabdos, a rod, and nema, a thread)

Frustules quadrangular, concatenate, composed of numerous septate partitions with transverse costæ or rows of puncta. Valves elliptical, with a pseudoraphe and transverse apparent costæ and punctate lines; the partitions with one or several foramina.

Chromatophores in rosettes of various kinds (Karsten); usually parallel to the septa.


Valve hyaline at the ends, with transverse rows of puncta producing the appearance of costæ between the rows; pseudoraphe distinct; foramen single.

Diatoma arcuatum Lyngbye.

Common along the coast.

Pl. 8, Figs. 1, 2, and 3; Pl. 40, Fig. 10.

According to T. H. Buffham (Jour. Quek. M. C., Series 2, Vol. 2, p. 131), the frustules are of two kinds, those in which the length and breadth are the same and those which are much lengthened, with a wide hyaline girdle frequently in the middle. At the time of fructification the smaller frustules are attached to a larger one which produces a sporangium at the end of the girdle from which the other end of the frustule has disappeared, or, if the two halves of the frustule remain, two sporangia are formed.


Frustules small; valve not smooth at the ends, elliptical or lanceolate-elliptical, with transverse rows of puncta; pseudoraphe distinct. Foramen single, alternating above and below in adjoining partitions.

Common in the blue clay and along the coast.

Pl. 8, Fig. 7 and Pl. 38, Fig. 11.


Valve linear-lanceolate, with smooth angles; rows of puncta transverse, the intervals appearing as costæ, as in arcuatum. Foramina, three.

Blue clay in the Pensauken and Pavonia deposits and along the coast.

Pl. 8, Figs. 4, 5 and 6.

Tabellaria Ehr. (1839)

(tabella, a tablet)

Frustules quadrangular, adnate in filaments, frequently found in zig-zag chains, united by a gelatinous isthmus, at length separating. Valve linear, inflated in the middle and at the ends; striæ transverse.

Chromatophores numerous, small, along the zones.


Valve elongated; pseudoraphe narrow; transverse striæ faint. In the zone view a straight septum is shown at each end of a valve.

Common, especially in the cedar swamps and ponds of the Pine Barren region, N. J.

Pl. 8, Figs. 11 and 12.


Valve linear, with median inflation larger than the terminal; pseudoraphe rather broad in the middle; transverse striæ subtly punctate. In zone view the frustules are quadrangular, or nearly so, with about six sometimes curved septa at one end alternating with those on the other end.

Conferva flocculosa Roth.

Common especially in the Pine Barrens of New Jersey.

Pl. 8, Figs. 8, 9 and 10.

Grammatophora Ehr. (1840)

(from gramma, a letter, and phoreo, I bear)

Frustules quadrangular, adnate, in zig-zag, united by an isthmus, or, usually, found free; divided by two sinuate and perforate curved septa. Valve linear or oblong, sometimes with sinuate sides, and with a pseudoraphe and transverse punctate lines.

Chromatophores granular.


Valve linear-elliptical, with smooth apices. Septum with a wide undulation near its origin, thence straight and incrassate at the end. Striæ in quincunx, 18-21 in 10 µ.

Diatoma marinum Lyngbye.

Blue clay. Along the coast.

Pl. 8, Figs. 17 and 18.


Valve linear, slightly constricted near the smooth apices. Septum undulated near its origin and then straight, incrassate at the end. Puncta in quincunx very subtle, 34-36 in 10 µ.

Grammatophora subtilissima Bail.

Grammatophora oceanica var. subtilissima (Bail.) V. H., according to De Toni. G. marina and G. oceanica are united by some authors; the latter has more subtle striæ.

Along the coast.

Pl. 8, Figs. 13 and 14.


Valve linear-elliptical, long, measuring to 150 µ (De Toni); smooth at the apices. Septum with numerous undulations and hooked at the apex. Puncta in quincunx, 17 in 10 µ.

Along the coast.

Pl. 8, Fig. 21.


Frustule nearly quadrate; valve with rounded but not smooth apices. Septum bent into a sharp angle near its origin and ending in a broad hook. Puncta in transverse rows, 14 in 10 µ.

Along the coast.

Pl. 8, Figs. 15 and 16.


Frustule oblong; valve elliptical-lanceolate. Septum robust with several undulations and hooked at the end. Pseudoraphe distinct; transverse rows of puncta, 10 in 10 µ.

Reported by Kuetzing in the Atlantic Ocean and by Kain at Belmar, N. J. I have not found it on our coast and I believe, in some cases, it has been confused with G. angulosa var. hamulifera. The figure is drawn from an Iceland form in H. L. Smith T. S., 186.

Pl. 8, Figs. 19 and 20.

Striatella Ag. (1832)

(dim. of stria, referring to the lines on the frustule)

Frustules tabulate, adnate in short, stipitate filaments, scarcely siliceous, divided into partitions, septate or partly so at alternate ends.


Frustules with numerous bent septa extending the entire length. Valve lanceolate, somewhat unsymmetrical, subtly punctate, with pseudoraphe quite distinct.

"The specific name is derived from the appearance of the endochrome which in the living specimen is invariably collected in a central mass with slender threads radiating in all directions toward the cell-wall" (Wm. Sm.). Pyrenoids cuneate, in the centre of the endochrome, numerous.

Long Island Sound and along the coast.

Pl. 8, Figs. 22 and 23.


Frustules quadrangular, with robust alternate septa extending to the middle. Puncta in quincunx, 22 in 10 µ.

Tessella interrupta Ehr.

Very rare along the coast.

Pl. 8, Fig. 24. (From a form found at Stonington, Conn.)

Attheya West (1860)

(named after Thomas Atthey)

Frustules quadrangular, tabulate, with numerous annuli. Valve elliptical-lanceolate, with a pseudoraphe and a central punctum. Extending from each end is a strong spine half as long as the valve.


The only species. Diagnosis of the genus. The valves are imperfectly siliceous, scarcely visible in balsam.

Very local. Abundant at Shark River, N. J.

Pl. 8, Fig. 25.


Valve symmetrical in zone and valve view along the sagittal line, but asymmetrical to the transverse axis, cuneate. In zone view sometimes with wedge-shaped septa. Valve finely striated, without central and usually without terminal nodules; a pseudoraphe present.

Licmophora.—Frustules cuneate in stipitate fan-shaped fascicles.

Meridion.—Frustules cuneate in spiral fascicles.

Licmophora Ag. (1827)

(licmos, a fan, and phoreo, I bear)

Frustules wedge-shaped, joined together into fan-shaped, stipitate fascicles. Valve cuneate, rounded at both ends, septate. Chromatophores granular, round or oval in our species.


(In accordance, so far as it relates to our species, with the classification of C. Mereschkowsky, Diagnoses of New Licmophoræ, Nuova Notarisia, 1901.)

Placatæ—valve narrow, striæ very fine, septa superficial flabellata
Dubiæ—valve bacilliform, septa shallow, frustule with thick walls ovulum
Paradoxæ—valve with lower end produced, striæ fine, pseudoraphe distinct, septa deep paradoxa
baileyi ?
Lyngbyeæ—valve narrow, attenuated at both ends, distinct, septa deep lyngbyei
Peristriatæ—valve broad, pseudoraphe wide, striæ robust ehrenbergii


Frustule elongate, narrow; valve narrow, lanceolate-cuneate, enlarged at the base; striæ very fine, 30 in 10 µ.

Echinella flabellata Carm.

Licmophora splendida Wm. Sm.

Common along the coast.

Pl. 9, Figs. 1 and 2.


Valve ovate, attenuated to the rounded inferior apex; pseudoraphe indistinct, striæ fine, 24 in 10 µ. Zone view broad, cuneate, angles rounded, inferior apex broad; frustule robust, septa superficial, straight. (Mereschkowsky, in part.)

Atlantic City. Common.

Pl. 9, Figs. 8 and 9.


Frustule broad, with rounded angles; septa curved; valve ovate, inferior apex produced. Pseudoraphe distinct; striæ varying from 25 below to 30 above in 10 µ.

Echinella paradoxa Lyng.

Rhipidophora paradoxa Kuetz.

Along the coast.

Pl. 9, Figs. 6 and 7.


Frustule cuneate, narrow, with sinuate margin; valve clavate, linear at the base; striæ, 20 to 22 in 10 µ.

New Rochelle. Along the coast.

Pl. 9, Fig. 11.


As in the type, but more graceful and with deeper septa.

Rhipidophora elongata Kuetz.

Along the coast. Not common.

Pl. 9, Figs. 12 and 13.


Frustules cuneate, narrow, usually found in twos. Valve clavate, hyaline, rather broad at the base; septa moderately deep; pseudoraphe indistinct; striæ, 27 at the base, 30 in the middle and 33 at the apex in 10 µ.

Gomphonema tinctum Ag.

Along the coast. Abundant from about the middle of July to the middle of August.

Pl. 9, Figs. 14 and 15.


Frustule broadly cuneate or with convex margins, rarely almost orbicular; valve spatulate or ovate with slender, produced base; septa very deep; pseudoraphe distinct; striæ 20 in 10 µ.

Podosphenia baileyi (Edw.) Lewis.

Long Island Sound and upper coast of New Jersey.

This form is placed in a doubtful position by Mereschkowsky. As it corresponds more closely to the Paradoxæ, it is placed here provisionally. The girdle face and apex of the valve are round, the pseudoraphe is distinct and the septa deep, but the stipe is short.

Pl. 9, Fig. 10 and Pl. 38, Figs. 3 and 4.


Frustule cuneate, slightly rounded at the angles. Valve oblanceolate; pseudoraphe distinct; septa deep; striæ, 12 in 10 µ below, and 16 in 10 µ above.

Podosphenia lyngbyei Kuetz.

Along the coast.

Pl. 9, Figs. 3 and 4.


Frustule cuneate, broad. Valve obovate-lanceolate; pseudoraphe wide; striæ coarse, 8 in 10 µ, moniliform.

Podosphenia ehrenbergii Kuetz.

Along the coast.

Pl. 9, Fig. 5.

Meridion Ag. (1824)

(merizo, I divide)

Frustules in zone view cuneate, adnate in circular or spiral fasciæ, at length becoming free. Valve symmetrical with respect to the longitudinal axis, more or less cuneate; costæ and striæ transverse.

Chromatophores numerous, small, elongated, in irregular rows on the zone (Pfitzer).


Transverse costæ coarse, variable in number and distance apart, sometimes interrupted or indistinct; striæ interstitial, 16 in 10 µ.

In springs and small streams of pure water.

Echinella circularis Grev.

Meridion constrictum Ralfs, sometimes given as a variety of M. circulare, differs only in the constriction below the apex. The two kinds of frustules are usually found growing together and as the variation is often extremely slight they are here included under the earlier name.

Pl. 10, Figs. 1, 2 and 3.

Fig. 1 represents the constricted form which is the more common. Fig. 3 is a sporangial form.

The sporangial frustules vary in shape and size, some being long and slender, others clavate, but they are all more or less tumid in the middle, with costæ more indefinite than in perfect valves. All gradations occur, one end becoming shorter until the valve has the shape of the variety known as constrictum. It would seem, therefore, that the non-constricted form is a passage from the sporangial to the smaller or adult form, or is of no specific importance. All forms are found living together. The adult frustules are the smaller ones; it is from them that the sporangia are produced.

Meridion intermedium H. L. Smith (Amer. Quart. Mic. Jour., Vol. 1, p. 12) is characterized by less evident costæ and is more delicate in general appearance. Some forms are capitate and others are not. Prof. Smith compares the M. intermedium with Peronia erinacea Bréb. and Arnott which he has named M. erinaceum, hitherto found only in Europe, and points out the relation of the two forms to Licmophora. An examination of the H. L. S. type slides of the two diatoms proves that Peronia has very delicate costæ and a distinct pseudoraphe not noticeable in Meridion. On the slide of Peronia are frustules exactly similar to certain of the sporangial variations of M. circulare.

The fan-like arrangement of Licmophora, the marine form, and the circular chains of Meridion, the fresh-water genus, are similar. Both are stipitate at the beginning of their growth.


Divided into three sections:

Diatominæ.—Valve circular, elliptical to linear, quadrate or cruciform, with transverse costæ; without raphe, a pseudoraphe sometimes wanting.

Fragilariinæ.—Valve elongate, with small central and terminal elevations, without costæ but with transverse punctate striæ; without genuine central nodule.

Eunotiinæ.—Valve lunate; a raphe sometimes partially formed with terminal nodules near the edges.


Diatoma.—Frustules in filaments. Valve linear or elliptical, costate.

Plagiogramma.—Frustules in fasciæ or free. Valve costate.

Opephora.—Valve costate, with an inner punctate stratum.

Diatoma De Candolle (1805) em. Heib. (1863)

(diatemno, I cut in two)

Frustules oblong or quadrate, adnate in filaments, attached by alternate angles and finally separating. Valve linear or elliptical, with transverse costæ and rows of puncta and a pseudoraphe.

Chromatophores large granules without definite arrangement. (See Pl. 40, Fig. 11.)


Valve elliptical-lanceolate, with apices sometimes rostrate or capitate; pseudoraphe narrow; costæ, 5 in 10 µ.

Common everywhere in pure fresh water and extremely variable.

Pl. 10, Figs. 9 and 10.

Var. elongatum (Ag.) = var. ehrenbergii (Kuetz.)—elliptical-lanceolate, constricted near the apex.

Var. grande (Wm. Sm.) Grun.—linear, elongated, constricted near the apices.

Pl. 10, Fig. 4.

Both of these varieties, with numerous intermediate forms, are abundant near Newtown Square. Varieties of Grunow, known as breve, ovate-lanceolate; productum, ovate-lanceolate with produced apices; capitulatum, lanceolate with capitate extremities, are mingled together in the same gathering.


Valve linear with rostrate apices; costæ robust; striæ delicate, 20 in 10 µ. Zone view quadrangular.

Common in fresh water.

Pl. 10, Figs. 5 and 6. Fig. 11, Pl. 40, shows frustules containing the nuclei and chromatophores.


Valve ovate-lanceolate to lanceolate; apices obtuse, not produced. Costæ not numerous, robust; striæ moniliform. Zone view quadrate, the costæ as septa deeply dividing the valve into convex elevations.

Common in springs.

Pl. 10, Figs. 7 and 8.

In all species of Diatoma a punctum, or pore, is observed, usually at alternate ends of the two valves, by means of which a communication exists between adjoining frustules and causes them to adhere in zig-zag chains when partially separated.

Plagiogramma Grev. (1859)

(plagios, on the side, and gramma, a letter)

Frustules quadrangular, adnate in fasciæ, or free. Valve linear, elliptical, or elliptical-lanceolate, divided by two or more median and two terminal costæ or with a central and two terminal hyaline spaces.

Valve with two median and two terminal costæ:
Linear, pseudoraphe distinct pygmæum
Linear, with striæ at the ends wallichianum
Ovate-lanceolate obesum
Valve without costæ but with central and terminal nodules: pseudoraphe absent tessellatum


Valve linear-elliptical; pseudoraphe distinct; rows of granules transverse, usually six in each compartment, moniliform, three on each side.

Blue clay. Not common.

Pl. 10, Fig. 13.


Valve linear, rounded at the ends; pseudoraphe absent; transverse rows of granules, six or seven in each compartment, and two or three rows of smaller granules at each end.

Blue clay. Not common.

Pl. 10, Fig. 14.


Valve rhombic-lanceolate, the costæ scarcely visible; pseudoraphe rather wide; rows of granules, about seven in each compartment, slightly radiating.

Blue clay. Not common.

Pl. 10, Fig. 12.


Valve elliptical-lanceolate; central space transversely elliptical to the major axis, half the diameter of the valve; terminal spaces more or less circular or ovate. Granular markings large, quadrangular, in transverse rows. Pseudoraphe not distinct. As the central space does not reach the margin, it is a question whether this form is a Plagiogramma or a new genus.

Blue clay. Rare.

Pl. 10, Fig. 11.

Opephora Petit (1888)

(ope, an opening, and phoreo)

Frustule rectangular. Valve cuneiform, linear or elliptical-lanceolate, with broad, transverse striæ and a well-defined pseudoraphe or median area.

The genus "portant des stries en forme de boutonnières," as Petit remarks, is quite near Fragilaria, under which the species here described were originally included. (See Schmidt's Atlas, Pl. 298, where numerous forms of F. pinnata are figured.)


Valve obovate-lanceolate or nearly linear with rounded apices; striæ transverse, broad, 3 or 4 in 10 µ; median area lanceolate.

An inner stratum, with puncta in transverse rows, is apparent.

Blue clay. Not uncommon. Variable in size.

Pl. 10, Figs. 16 and 19.


Valve linear, oblong, with rounded apices. Median area linear, narrow; striæ punctate.

Blue clay.

Pl. 10, Fig. 18.

Petit (Diat. Cap Horn) in his diagnosis states that the valves are cuneiform, but they are not always so.


Valve lanceolate; costæ slightly radiate, punctate; median area broad, lanceolate.

Differs from O. pinnata in outline, radiation of the costæ and median area.

Blue clay. Rare.

Pl. 10, Fig. 17.


Fragilaria.—Frustules in fasciæ. Valve with transverse striæ. Pseudoraphe indistinct.

Rhaphoneis.—Striæ radiate; pseudoraphe distinct.

Dimerogramma.—Pseudoraphe broad.

Trachysphenia.—Valve cuneiform.

Synedra.—Valve elongate.

Asterionella.—Frustules in star-shaped clusters.

Fragilaria (Lyng.) Rab.

(fragilis, because of the fasciæ easily breaking up)

Frustules rectangular, adnate in fasciæ, soon breaking up. Valve lanceolate, oblong or elliptical in general outline, with convex or sinuate margins; without costæ; pseudoraphe narrow or indistinct; striæ transverse. Chromatophores vary according to species. In some they consist of four bands on the valves; in others they are granular (Mereschkowsky).

Brun divides the genus into two sections, Fragilaria proper and Staurosira. The former, with an indistinct pseudoraphe, includes the species virescens, arctica, undata and linearis, while the latter, with distinct pseudoraphe, includes capucina, harrisonii, construens and parasitica.


Frustules in long fasciæ. Valve elliptical-lanceolate, obtuse at the apices; pseudoraphe indistinct; striæ, 17 in 10 µ, punctate.

Very common in springs and pure streams. The fasciæ are often a foot or more in length.

Pl. 10, Figs. 20 and 21.


Valve oblong or elliptical, 10 µ in length; striæ subtle, with coarse, short striæ at intervals on the margin and evident in zone view.

Marine. Common at Cape May, N. J.

Pl. 10, Figs. 22 and 23.


Valve in general outline linear-elliptical, with extremities produced; striæ subtle; pseudoraphe distinct.

Fresh water.

Pl. 10, Figs. 24, 25, 27, 28 and 29.


Valve linear, with rounded apices; striæ subtle; pseudoraphe indistinct.

Marine. Cape May.

Pl. 10, Fig. 37. Fig. 36 is an indeterminate form occasionally found in the blue clay.


Valve linear, constricted at the hyaline middle; apices slightly produced; striæ, 17 in 10 µ. Quite variable in size.

Schuylkill River. Morrisville (Keeley).

Pl. 10, Fig. 34.


Frustules rectangular, solitary or in twos. Valve cruciform; pseudoraphe narrow, lanceolate; striæ robust, radiating in the middle, composed of confluent puncta, larger at the circumference.

Blue clay.

Pl. 10, Fig. 31.


Valve in general outline lanceolate, with produced apices; pseudoraphe lanceolate, distinct or broad; striæ subtle, 15 in 10 µ. L. of valve, 10-45 µ.

Staurosira construens Ehr.

Odontidium tabellaria Wm. Sm.

Blue clay.

Pl. 10, Fig. 30.


Frustules solitary or in twos. Valve lanceolate, sometimes constricted in the middle; pseudoraphe wide, lanceolate; striæ subtle. Parasitic on other diatoms.

Odontidium parasiticum Wm. Sm.

Not common. Media (Palmer).

In the constricted form it is known as F. construens var. binodis (Ehr.) Grun.

Pl. 10, Fig. 35.

An examination of the synonymy of the species of Fragilaria will convince the student of the difficulty of determining the correct name even in well-known forms. If all of the species of Fragilaria proper have granular chromatophores, and all of Staurosira are placcochromatic, a satisfactory division can be made, but so long as these facts are not known in all species, and as authors have repeatedly confused the two divisions, the nomenclature will be uncertain. F. harrisonii is probably in any case to be separated from the others. De Toni includes it under its original name of Odontidium, which genus he places near to Diatoma. The number of species in our locality is too limited to render further discussion of any value.

Rhaphoneis Ehr. (1844)

(rhaphis, a needle)

Frustule in zone view linear. Valve lanceolate or elliptical-lanceolate; pseudoraphe distinct; striæ radiating, moniliform.


Valve lanceolate, broad, with apices produced; striæ in curved lines, moniliform, the large granules in longitudinal lines.

Blue clay.

Pl. 10, Fig. 38.


Valve as in type form but shorter, with larger and more remote granules.

Blue clay.

Pl. 10, Figs. 39 and 40.


Valve lanceolate, rostrate; granules in longitudinal and nearly transverse, not radiating, lines.

Absecon, N. J.

Pl. 10, Fig. 41.

Dimerogramma Ralfs (1861)

(dis, two, meros, a part, gramma, a letter)

Frustules quadrangular, inflated at the angles, in fasciæ. Valve ovate or lanceolate; striæ moniliform, transverse or slightly radiate; median area or pseudoraphe broad, lanceolate.


Valve lanceolate or linear and inflated in the middle; striæ moniliform, transverse or slightly radiate; median area linear or lanceolate, sometimes not reaching the smooth extremities; striæ, 8 in 10 µ.

Pl. 12, Figs. 9 and 10.

Fig. 9 differs in its lanceolate outline, in having four puncta on each side in a row, and in the striæ which are radiate.


Valve elliptical-lanceolate, with rounded apices; striæ moniliform, radiate; pseudoraphe narrow, lanceolate.

Blue clay.

Pl. 12, Fig. 11.


Valve rhombic-lanceolate; striæ punctate, radiate; pseudoraphe lanceolate; apices smooth.

Blue clay. Along the coast.

Pl. 12, Figs. 12, 13, 14.

Trachysphenia Petit (1877)

(trachys, rough, and sphen, a wedge)

Frustules rectangular. Valve cuneiform with coarse puncta in transverse and longitudinal lines; pseudoraphe narrow, linear. One species only.


Characters of the genus. Valve small; puncta, 6 in 10 µ. Allied to Dimerogramma.

Shark River, N. J. Rare.

Pl. 12, Fig. 15.

Synedra Ehr. (1830)

(synedrion, a sitting together)

Frustules adnate in small stipitate clusters or free. Valve elongate, linear or linear-lanceolate; pseudoraphe distinct; costæ absent.

The genus Synedra has few distinctive characters. As Brun remarks (Diat. des Alpes et du Jura, p. 122), the dilatation of the extremities and the pseudo-nodule are of little value in classification, as the intermediate forms are so numerous. Fragilaria occurs in very long ribbons or fasciæ, Synedra in short fasciæ or radiating clusters. Fragilaria is seldom longer than three or four times the width, while Synedra is nearly always so. The former has fine, often subtle, markings and narrow pseudoraphe, while the latter has coarser punctate striæ and a more distinct pseudoraphe.

Chromatophores usually consist of two bands, one on each of the valves. Karsten states that in the marine forms the chromatophores are oval or polygonal discs, each of which usually encloses a pyrenoid.


Frustules solitary or in twos. Valve 150-250 µ in length, linear or linear-lanceolate, with rostrate apices; striæ, 9 in 10 µ.

Common in rivers and streams.

Pl. 11, Figs. 4, 7 and 11 (?).

Frequently interrupted in the middle. The distinction made by Wm. Smith as to the presence or absence of the central blank space is probably not necessary, as both forms are found which are otherwise identical.

Fig. 5 represents the formation of a sporangial frustule which differs from the usual form in its inflated ends prolonged into rostrate apices. Figs. 1 and 6 are sporangial frustules.


Valve sublanceolate, inflated at the ends, apices rounded; central space not always distinct; pseudoraphe narrow; striæ radiate at the ends.

This is not Kuetzing's species, if the descriptions and figures are accepted, nor is it H. L. Smith's Type No. 545, which is S. ulna var. danica, nor is it S. biceps Wm. Smith, but it is exactly Schmidt's form (Atlas, Pl. 303, Figs. 10-15).

Schuylkill River.

Pl. 11, Fig. 3.


Valve lanceolate, suddenly constricted at the rounded apices; central space frequently absent.

Very common in streams.

Pl. 11, Fig. 2.

The figure represents an unusually large form. It differs from S. ulna only in its apices.


Valve long, linear, dilated into triangular acute apices; pseudoraphe distinct; striæ radiate at the ends.

Blue clay.

Pl. 11, Fig. 8.


Valve very narrow, lanceolate, acicular, with obtuse apices.

Common in the Schuylkill River.

Pl. 11, Figs. 9 and 18.


Valve constricted in the middle; apices sub-acute, sometimes slightly rostrate or capitate; central space evident.

Neshaminy Creek (Palmer). Blue clay. Crum Creek.

Pl. 11, Figs. 12 and 13.


Valve lanceolate, tapering to the sub-acute, rostrate or slightly capitate apices; dilated at the central hyaline space; pseudoraphe distinct. Very variable in size.

Crum Creek. Schuylkill River. Rather common.

Pl. 11, Figs. 14, 15, 16.


Valve as in type form, except that one end is curved like a beak, as in S. hamata Wm. Sm., which it resembles.

Not uncommon in the Schuylkill River.

Pl. 11, Fig. 17.


Valve linear-lanceolate with produced rostrate apices, asymmetrical, sigmoid; pseudoraphe narrow; pseudo-nodule large.

Common in fresh water.

Pl. 12, Fig. 1.


Frustule slightly attenuated at the ends, truncate, somewhat tumid in the middle and flexed. Valve lanceolate, with obtuse or subcapitate apices and with two almost imperceptible constrictions at the middle producing a tumid appearance; pseudoraphe distinct; pseudo-nodule absent. L. 56 µ; striæ, 14-16 in 10 µ.

Some valves are bent and incised on one side. The outline of the valve is that of pulchella.

Common at Newtown Square.

Pl. 12, Fig. 2.


Frustules linear, in small fasciæ. Valve 34 µ in length, linear, with apices rostrate, obtuse, sometimes slightly capitate; pseudoraphe distinct; striæ about 20 in 10 µ.

Fresh water.

Pl. 10, Figs. 32 and 33.

There is difficulty in recognizing S. radians K. as described and figured by different authors. On Plate 12, Fig. 8, I have drawn a specimen from H. L. Smith's Type Slide No. 574, labelled S. radians Kuetz., not Wm. Smith, which, however, corresponds closely to Smith's figure (Brit. Diat. 1, Pl. 11, Fig. 89). De Toni gives S. radians Kuetz. as equivalent to S. tenera Wm. Sm. Van Heurck's figure of S. radians, and also the figure of ulna var., said to be synonymous with H. L. Smith's S. radians, which does not correspond to the specimens on Smith's slide in my possession, are confusing. In Van Heurck's Synopsis the striæ are said to be 16 or 17, while De Toni describes them as subtle and from 17 to 24 in 10 µ. The length is quite variable.

Several species of Synedra resemble S. radians in the mode of growth, as they are adnate at first, in short bands, the frustules being sessile on other plants or objects, attached at the terminal nodules which, although scarcely visible in most forms, are probably present in all. The frustules are not closely connected at the free end, and soon become entirely detached.

In Diatoma and Fragilaria, we find a punctum or pore at one end of a valve, but not in line with the pseudoraphe; in Synedra, a minute pore is usually found in the position of the terminal nodule and, in some species, indications of a central nodule are observed; the median line is wider but there is no raphe. In the fresh-water Synedræ, many of which are among the longest of diatoms, living in running streams, the terminal nodules are much more indistinct, while the marine forms have distinct terminal nodules, are not, as a rule, found in bands, and assume a more naviculoid outline.


Valve lanceolate, with produced or rostrate apices; pseudo-nodule wide, excentric. L. 17 µ.

Crum Creek.

Pl. 12, Fig. 5.

Fig. 6 represents a variety with coarser striæ from the Schuylkill River. Both are easily mistaken for Fragilaria intermedia.


Frustules geminate or flabellate on a stipe. Valve slightly inflated in the middle and at the apices; pseudoraphe narrow; striæ finely punctate, radiate at the ends.

Marine. Atlantic City.

Pl. 11, Fig. 10.


Valve lanceolate; striæ marginal, leaving a broad lanceolate pseudoraphe.

Common along the coast.

Pl. 12, Fig. 3.


Valve lanceolate, slender; striæ marginal, shorter than in the type.

Synedra gracilis Kuetz.

Common along the coast.

Pl. 12, Fig. 7.


Valve linear-lanceolate; striæ, 11 in 10 µ, very short.

Not common. New Rochelle.

Pl. 12, Fig. 4.

Asterionella Hassall (1855)

(dim. of aster, a star)

Frustules linear, slightly inflated at the ends, arranged in star-shaped clusters which soon break up. Valve linear, unequally inflated at the ends.


Valve clavate at the ends; striæ transverse, 17 in 10 µ, pseudoraphe very narrow or indistinct; an ovoid, hyaline area at each end.

Newark, N. J. Broomall's Lake, Media (Palmer).

Pl. 12, Figs. 19, 20, 21.


Valve linear, capitate at each end and tumid in the middle; striæ distinctly punctate; pseudoraphe indistinct, or not apparent. L. 30 µ.

Fresh water. May's Landing, N. J.

Pl. 12, Fig. 22.


Eunotia.—Frustules either free, in fasciæ or epiphytic. Valves arcuate.

Actinella.—Frustules, solitary or in small clusters, cuneate. Valve inflated at one end.

Eunotia Ehr. (1837) em. Grun. (1862)

(eu, well, and noton, a back, referring to the strong, ridged dorsum)

Frustules free, in fasciæ or epiphytic. Valve arcuate, without costæ, transversely striated; pseudoraphe absent; pseudo-nodules at each end.

Chromatophores laminate along the concave zone and the valves.

Very many species of Eunotia have been created to differentiate size and number of crenæ or undulations. An examination of certain fossil deposits of New England, as well as a gathering from the blue clay of Philadelphia, will show forms which vary infinitely. E. major and E. gracilis are scarcely distinguishable because of the intermediate variations. The striæ in all forms are punctate, but the puncta are frequently confluent.


Eunotia is divided into two sections, Himantidium and Eunotia proper. In Himantidium, the frustules are in fasciæ, either short or long. Among those with short fasciæ are major, gracilis, and nymanniana; those with long fasciæ are pectinalis, solierolii and veneris. Eunotia proper includes frustules, free or epiphytic, in which the valves are not dentate on the dorsal margin, such as lunaris, hemicyclus, biceps and prærupta; and those in which the valves are dentate or crenate on the dorsum, such as monodon, triodon, diadema and others.

The resemblance between Eunotia and Epithemia is noticeable. In both, the epiphytic character of the valve is seen in the shape of the frustule which is arched, and, in the free forms, is adherent at the ends only. In Epithemia, the median is more evident than the terminal nodules. In Eunotia, there is no median nodule, but the end nodules, in some species, are quite evident, and a tendency is shown to produce a very short raphe. The arrangement of puncta in valve view is similar in both genera.

Section 1. Himantidium


Valve arcuate, linear, subcapitate, recurved. Striæ punctate, 12 in 10 µ L. 90-190 µ.

Common in fresh water.

Pl. 13, Figs. 1 and 2.


Valve with sides parallel; apices slightly capitate and revolute; striæ, 10 in 10 µ. The striæ on the connective membrane more delicate than in E. major. Intermediate forms occur.

Common in fresh water.

Pl. 13, Fig. 3. Fig. 4 is indeterminate.


Valve small, curved, with parallel dorsal and ventral margins; apices truncate and recurved into dorsal elevations; striæ delicate.

Blue clay. Not common.

Pl. 13, Fig. 32.


Valve linear, arcuate, apices slightly rostrate; striæ distinctly punctate with puncta in longitudinal rows nearer together at the ends.

Himantidium pectinale Kuetz.

Common in fresh water.

Pl. 13, Figs. 6 and 7.

The fasciæ are associated in large masses, sometimes an inch or more in diameter, and late in August are found a foot or more in length, of a beautiful chocolate color. Exceedingly abundant in the cedar-swamp streams of the Pine Barren regions of New Jersey. In winter, the dead frustules form a parchment-like coating upon the twigs, dead leaves, and other débris on the borders of streams.

This species can scarcely be referred to Dillwyn's Conferva pectinalis, as, in his description, quoting Mueller, he says that "the filaments are of a dirty green color; seldom exceeding half an inch in length." Dillwyn's form is probably Fragilaria virescens, which equals Fragilaria pectinalis Ehr., while Kuetzing's species is Fragilaria pectinalis Ralfs. It is not impossible to confuse Fragilaria virescens and Eunotia pectinalis when the zone only is seen under a low power and their mode of growth is similar.


Valve as in type form, but with undulate margins.

Common in the cedar swamps of New Jersey.

Pl. 13, Figs. 8 and 10.


Valve as in type, but with internal divisions as though in the process of reduplication.

Not common. Moorestown, N. J. (Palmer).

Pl. 13, Fig. 9.


As in type, but with the valves tumid in the middle.

May's Landing, N. J.

Pl. 13, Fig. 12.

Fig. 11 is a form found in the blue clay. It differs in the coarser puncta from the var. ventricosa. In outline it resembles Eunotia arcus Wm. Sm., which is Ceratoneis arcus (Ehr.) Kuetz., but the central nodule is not present as in the latter form, which connects Eunotia and Cymbella. It may be a form of E. luna Ehr. (A. S., Atlas, Pl. 286, Figs. 33 and 34.)


Valve with convex dorsal and straight ventral margins, more or less constricted near the sub-acute apices. Striæ subtle, punctate.

Eunotia incisa Greg.

May's Landing, N. J. Blue clay, Pavonia, N. J.

Pl. 13, Figs. 30 and 31.

Eunotia (proper)


Frustules sessile, solitary or in clusters. Valve arcuate, narrow, attenuated toward the apices, which are sometimes slightly rostrate or rostrate-capitate; transverse striæ, 14 in 10 µ, punctate.

Very common in ditches, especially in the spring. Variable in length.

Pl. 12, Figs. 24 and 25.


Valve semicircular, with obtuse apices; striæ transverse, punctate; terminal nodules minute and indistinct.

Hammonton Pond, N. J. Rare.

Pl. 12, Fig. 23.

The genus Pseudo-Eunotia was created by Grunow for forms like Eunotia, but without terminal nodules. As, however, in E. lunaris and E. hemicyclus nodules are evident, although not so large as in many species, I include these two forms as heretofore under Eunotia.


Valve linear, slightly arcuate, narrow, with rounded apices somewhat revolute; striæ, 16 in 10 µ.

May's Landing, N. J.

Pl. 13, Fig. 27.


Valve convex on dorsal side, apices dilated and truncate; striæ distant at centre.

Common in the blue clay.

Pl. 13, Fig. 5.


Valve with two undulations; otherwise as in type.

Eunotia bigibba Greg.

With the type.

Pl. 13, Fig. 19.


Valve arcuate, with several or numerous dorsal ridges or crenæ which decrease in relative size in proportion to their number. Striæ radiate, variable in distance apart, and in size of puncta.

Ralfs included under this one name the following species named by Ehrenberg: E. diodon (2 crenæ); E. triodon (3); E. tetraodon (4); E. pentodon (5); E. diadema (6); E. heptodon (7); E. octodon (8); E. enneadon (9); E. decadon (10); E. hendecadon (11); E. duodecadon (12); E. serra (13); E. prioritis (14); all more than 20, E. polyodon. E. scalaris, with from 15 to 17 crenæ, and E. icosodon with 20, may be added.

It is probable that all of these forms occur at May's Landing, N. J. The forms with more than eight crenæ are comparatively rare. In the blue clay those with from four to six are most common.

Pl. 13, Figs. 13, 14, 15, 16, 17, 21, 24, 25.


Valve linear, apices revolute, acute, dentate on the dorsal margin, with one acute crena near each end.

Tom's River, N. J. Rare.

Pl. 13, Fig. 18.


Valve with straight ventral margin, and with two undulations on the dorsum; apices large, rounded.

May's Landing, N. J. Rare.

Pl. 13, Fig. 20 (not Schumann's form, which has angular crenæ).


Valve turgid in the middle and at the apices which are unilaterally truncate.

Pensauken, N. J. (artesian well).

Pl. 13, Fig. 26 (not a typical form).

The following are forms which appear to be indeterminate, or, in any case, are scarcely worthy of distinction by specific names, as might be said of others of the innumerable variations of this genus:

Fig. 23, Pl. 13, probably a form of prærupta. Newtown Square.

Fig. 28, Pl. 13, from the blue clay.

Fig. 29, Pl. 13, an asymmetrical form, apparently abnormal, but not rare at May's Landing, N. J.

Fig. 17, Pl. 38. Valve convex on the dorsal side, incised on the ventral; striæ about 15 in 10 µ, closer at the ends; L. 30 µ. Schuylkill River.

Fig. 18, Pl. 38. Valve arcuate, asymmetrical, broader at one end; terminal nodules large; striæ, 10 in 10 µ; L. 47 µ. Gloucester, N. J., artesian well.

Numerous variations of the above species are illustrated in Schmidt (Atlas, Pls. 285-291).

Actinella Lewis (1865)

(dim. of actin, a ray)

Frustules solitary, or in small clusters, sub-cuneate or nearly linear. Valve arcuate, rounded at one end and suddenly widened at the other into a cup-shaped or lychnoid inflation.


Valve with fine, transverse striæ; on the margin, puncta at intervals; terminal nodules distinct.

May's Landing, N. J.

Pl. 12, Figs. 16, 17, 18.

Fig. 17, from Tom's River, N. J., is an approach toward A. brasiliensis Grun.

Fig. 18 represents the frustules geminate, a frequent occurrence.