Section 3.--Encyonema. Frustules in Tubes

CYMBELLA VENTRICOSA KUETZ.

Valve lunate, with straight or slightly gibbous ventral margin; axial area indistinct; median line straight or nearly so; striæ punctate.

Very common, but extremely variable. The ventral margin is sometimes straight and sometimes quite gibbous.

Pl. 18, Figs. 14, 22; Pl. 38, Fig. 16; Pl. 40, Fig. 8.

{63}C. ventricosa is considered by some authors to be equivalent to C. affinis var. semicircularis Lagerst., Encyonema prostratum (Berk.) Ralfs, E. cæspitosum Kuetz. and E. auerswaldii Rab. H. L. Smith's Type Slide of C. ventricosa Ag. is said to equal C. affinis Kuetz., but the specimens appear to me to be equivalent to C. ventricosa Kuetz. Cleve unites many forms, including E. cæspitosum, under C. ventricosa.

CYMBELLA PROSTRATA (BERK.) CL.

Valve semi-elliptical, obtuse at the apices, which are sometimes prolonged and turned downwards; median line straight, terminal nodules distant from the ends; axial area narrow, central area rounded; striæ in radiating, slightly curved lines, indistinctly punctate.

Common in fresh water; occasional in brackish.

Pl. 18, Fig. 21 (represents a frequent variation).

CYMBELLA PHILADELPHICA N. SP.

Valve semi-elliptical-lanceolate, with rounded apices; ventral margin strongly gibbous; terminal nodules distant from the ends; axial area broad, central area widened on the dorsal side; striæ radiate, not curved nor of unequal length, indistinctly punctate, 10 in 10 µ on the dorsal, 8 in 10 µ on the ventral side. L. 86 µ.

This form approaches Encyonema prostratum (Berk.) Ralfs, Schmidt's Atlas, Pl. 71, Fig. 7, but differs in the striæ and the axial and central areas.

Blue clay of Philadelphia. Rare.

Pl. 18, Fig. 8.

CYMBELLA TRIANGULUM (EHR.) CL.

Valve semi-elliptical, with acute ends; median line straight; ventral side half the width of the dorsal, with straight, slightly convex or concave margin; striæ radiate, coarsely punctate.

Gloeonema triangulum Ehr.

Baker's Run, Willistown, Pa.

Pl. 18, Fig. 24.

CYMBELLA TURGIDA (GREG.) CL.

Valve semi-elliptical, with acute ends; ventral margin gibbous; ventral side half the width of the dorsal; median line straight; terminal fissures turned downwards; axial area broad; striæ radiate, coarsely punctate.

Baker's Run, Willistown, Pa.

Pl. 18, Fig. 23.

CYMBELLA TURGIDA (GREG.) CL. VAR. ?

Valve lunate, with gibbous ventral margin; median line straight; terminal fissures turned downwards near the ends; axial area lanceolate, striæ radiate on the dorsal side, 8 in 10 µ, punctate, 9 on the ventral side, closer at the ends where they are convergent. L. 65 µ. Not a typical form.

Willistown, Pa.

Pl. 18, Fig. 12.

CYMBELLA RHOMBOIDEA N. SP.

Valve rhomboidal, with acute ends; dorsal part one and a half times the width of the ventral; median line nearly straight, with terminal fissures turned downwards near the ends; axial area broad, not widened in the middle, except slightly on the ventral side; striæ {64}radiate, distant in the middle of the dorsal side where they are 7 in 10 µ, coarsely punctate, the puncta in longitudinal lines, 9 in 10 µ on the ventral side, closer at the ends. L. 69 µ.

Baker's Run, Willistown, Pa.

Pl. 18, Fig. 11.

CYMBELLA GRACILIS (RAB.) CL.

Valve semi-lanceolate, with acute ends; median line nearly straight, with terminal fissures turned downwards, distant from the ends; axial area linear; ventral margin straight or slightly gibbous in the middle.

Hammonton Pond, N. J.

Pl. 18, Fig. 20.

CYMBELLA LACUSTRIS (AG.) CL.

Valve elliptical-lanceolate, with obtuse ends, nearly symmetrical; median line straight, terminal fissures distant from the ends; striæ radiate in the middle, convergent at the ends, coarsely lineate.

Belmar, N. J.

Pl. 18, Fig. 25.

AMPHORA EHR. (1840)

(amphora, a jar)

Valves asymmetrical along the longitudinal axis, as in Cymbella, but with the plane passing through the dorsal and ventral sides of one valve at an angle with that of the other. As Cleve states, Cymbella and Amphora are forms of Navicula "with both valves similar and asymmetrical along the longitudinal axis," and the difference between Cymbella and Amphora is in the "degree of asymmetry." If, following H. L. Smith's diagrams (Lens, Vol. 2, 1873, p. 66), we assume that the usual form of the valve in Navicula is elliptical or lanceolate, and the zone view is rectangular, we have in Cymbella an arcuate median line and a more or less reniform valve, while the zone view remains rectangular with the valves parallel. Now, if the valves are asymmetrical along the longitudinal axis, and one side of one valve is separated from the corresponding side of the opposite valve by a wider connective zone than is the case on the other side, the transverse section of the frustule will appear cuneate, as in Amphora, and the connective zone will be wider on one side than the other. When, therefore, we examine an entire frustule as it is usually seen, we shall find the two raphes of the valves in focus at the same time on the ventral side, and, by changing the focus, the convex sides of the same valves are seen, the dorsal view with, usually, a wider connective zone. As an illustration, compare Figs. 5 and 6, on Plate 15, Fig. 6 being the ventral, and Fig. 5 the dorsal view.

As Amphoræ are epiphytic or parasitic, they are considered, as Cleve remarks, like Achnanthes and Cocconeis, as "degenerated forms."

Chromatophores usually single, lying on the ventral connective zone. Mereschkowsky describes nine forms.

Cleve divides the genus into a number of groups as follows:

Amphora proper.--Connective zone not complex; valves with longitudinal lines on the dorsal side; coarsely punctate or costate.

Diplamphora.--Zone complex; otherwise as in Amphora.

Halamphora.--Longitudinal lines absent; frustule elongate, with protracted ends.

{65}Oxyamphora.--Zone complex; longitudinal lines absent; frustule elliptical; valve lunate, with or without a central stauros; striæ punctate.

Amblyamphora.--Zone complex; frustule rectangular; valve lunate; striæ punctate; axial and central areas indistinct.

Psammamphora.--Zone not complex; frustule rectangular; central nodule frequently dilated to a stauros; no axial or central area.

Cymbamphora.--Valve semi-lanceolate; median line straight, approximate to the ventral margin.

AMPHORA

AMPHORA ROBUSTA GREG.

Frustule elliptical, truncate; valve lunate, with straight ventral margin; median line biarcuate; ventral side with coarse, radiate striæ, 6 in 10 µ, on both sides of the median line.

Along the coast.

Pl. 15, Fig. 1.

AMPHORA PROTEUS GREG.

Frustule elliptical, truncate; valve lunate, with straight ventral margin; median line biarcuate; no central area. Striæ on the dorsal side not interrupted, 9 in 10 µ. Ventral side striate toward the ends.

Differs from A. robusta chiefly in size and coarseness of puncta. Extremely variable in size.

Common along the coast.

Pl. 15, Figs. 5, 6, and 19.

AMPHORA OVALIS (BRÉB.) KUETZ.

Frustule elliptical, truncate; valve lunate; median line biarcuate; striæ on dorsal side 10-16 in 10 µ.

Var. libyca (Ehr.) Cl.--Central area distinct on the dorsal side.

Var. pediculus (Kuetz.) Cl.--Central area and nodule quite distinct. Striæ finer than in var. libyca.

Common in ponds. Quite variable.

Pl. 15, Fig. 7.

AMPHORA GIGANTEA VAR. FUSCA A. S.

Frustule elliptical; valve lunate, with straight ventral margin. Axial area absent on the dorsal side; dorsal striæ, 10 in 10 µ, punctate. Ventral part hyaline except at the ends, which are obliquely striated, with short, punctate lines. L. 70-120 µ.

Absecon, N. J.

Pl. 38, Fig. 1.

DIPLAMPHORA

AMPHORA CRASSA GREG.

Valve linear-elliptical, with obtuse, incurved ends. Median line biarcuate. Axial and central areas indistinct on the dorsal side; striæ coarsely punctate, interrupted by a longitudinal line on the dorsal side.

Along the coast.

Pl. 15, Fig. 3.

{66}AMPHORA AREOLATA GRUN.

Valve with straight ventral margin; median line straight, approximate to the ventral margin; axial area indistinct; several longitudinal lines crossed by apparent costæ which alternate with rows of fine puncta.

Blue clay. Rare.

Pl. 15, Fig. 11.

HALAMPHORA

AMPHORA COFFÆIFORMIS (AG.) KUETZ.

Frustule lanceolate, truncate; zone with numerous divisions. Valve arcuate on the dorsal and nearly straight on the ventral side; ends protracted or slightly capitate.

A. aponina Kuetz.

A. salina Wm. Sm.

Along the coast.

Pl. 15, Figs. 8 and 18.

OXYAMPHORA

AMPHORA LINEOLATA EHR.

Frustule membranaceous, elliptical, truncate, with broad ends. Zone with numerous divisions. Dorsal part striated transversely; ventral side with longitudinal lines.

A. plicata Greg.

A. hyalina H. L. Smith, Type No. 64.

Along the coast.

Pl. 15, Figs. 9 and 10.

AMPHORA OSTREARIA BRÉB.

Frustule oblong, with rounded angles. Zone with five or more divisions transversely striated. Central area narrow, biarcuate; central nodule dilated to a stauros. Valve narrow, with arcuate dorsal and straight ventral margin, acute at the ends. Striæ transverse, finely punctate.

A. vitræa Cl.; A. porcellus Kitton; A. quadrata Bréb.; A. elegans Greg. Appearance varies according to the position of the valve.

Along the coast.

Pl. 15, Figs. 12 and 21.

AMPHORA LÆVIS GREG.

Frustule oblong, hyaline and membranaceous. Valve linear or slightly arcuate, with ventral margin tumid in the middle; ends obtuse; central nodule dilated to a stauros; median line very narrow, biarcuate, coinciding with the dorsal margin at the ends; striæ transverse, punctate.

Blue clay.

Pl. 15, Fig. 13.

AMPHORA ACUTA GREG.

Valve lunate, with acute ends; ventral margin straight; ventral side very narrow. Central nodule dilated to a stauros; striæ transverse, punctate.

Along the coast.

Pl. 15, Fig. 20.

{67}AMBLYAMPHORA

AMPHORA OBTUSA GREG.

Frustule rectangular. Valve linear, obliquely rounded at the ends, with arcuate dorsal, and straight ventral, margin; median line biarcuate; striæ, 18-20 in 10 µ.

Along the coast. Common.

Pl. 15, Fig. 4.

PSAMMAMPHORA

AMPHORA ARENARIA DONK.

Frustule hyaline, rectangular, slightly tumid in the middle, with rounded angles. Valve linear with broad ventral side and straight or sinuate ventral margin. Striæ, 24-27 in 10 µ (Cleve).

Common along the coast.

Pl. 15, Fig. 17.

The distinction between A. obtusa and A. arenaria is not always evident if the valves alone are seen. The former has a complex zone, the latter a simple zone, and the valve has finer striæ. Cleve's descriptions and references in regard to these two forms do not agree with the descriptions and figures of H. L. Smith, or with the figures of Schmidt. The valves of most Amphoræ are capable of assuming various outlines according to their position.

AMPHORA OCELLATA VAR. CINGULATA CLEVE

Frustule rectangular. Valve linear, with dorsal margin arcuate and the ventral margin straight. Central nodule with a stauros on the dorsal side.

Squan River, N. J.

Pl. 15, Figs. 14 and 15.

CYMBAMPHORA

AMPHORA ANGUSTA VAR. EULENSTEINII GRUN.

Valve lanceolate, acute at the ends. Median line straight, approximate to the margin. Axial area widened on the dorsal side, indistinct on the ventral; striæ punctate.

A. eulensteinii A. S.

Common along the coast.

Pl. 15, Fig. 16.

On Pl. 40, Figs. 21, 22, and 23, I have attempted, imitating H. L. Smith's figures (Lens, l.c.), to illustrate the difference in the transverse sections of Navicula, Cymbella and Amphora.

Fig. 21 represents the transverse section of a convex Navicula, in which the valves ecg and fdh are parallel, and the median nodules c and d are central.

Fig. 22 is a transverse section of Cymbella in which the valves are nearly parallel and the median nodules are excentric. The girdles on one side, ea and af, are narrower than gb and bh on the other side.

Fig. 23 is a transverse section of an Amphora in which the valves appear in zone view with the median nodules of both valves on the same side. The girdles on the ventral side, ea and af, are narrower than gb and bh on the dorsal side. The girdles on the dorsal side are seldom as broad as gb and bh, the valve extending over a great part of the dorsal side to g' and h'.

{68}AMPHIPRORA EHR. (1843)

(amphi, on both ends, and prora, a prow)

Frustule twisted in the longitudinal axis, constricted in the middle; zone complex, with numerous divisions crossed by fine striæ. Valve lanceolate, acute. The raphe confined within a sigmoid keel or extension of the valve; the central and terminal nodules indistinct. Striæ transverse, punctate, with coarser striæ at the junction of the keel and lower part of the valve.

Chromatophores single, with indented border except in A. pulchra, in which there are two chromatophores with entire borders.

AMPHIPRORA ALATA KUETZ.

Frustule with a row of puncta at the junction line. Valve linear, acute at the ends. Median line sigmoid. Striæ lineate on the lower part of the valve, punctate on the keel.

Along the coast. Not common.

Pl. 14, Fig. 3.

AMPHIPRORA PULCHRA BAIL.

Frustule with sigmoid connective zone. Valve very convex, with sinuate keel and junction lines evident. In zone view and in valve view, one half of the frustule, owing to the elevation of the keel, is wider than the other half. Striæ punctate, coarser on the keel.

Not uncommon along the coast.

Pl. 14, Figs. 1 and 2.

AMPHIPRORA CONSPICUA GREV.

Valve linear or elliptical, with acute ends. Median line sigmoid, but the junction lines not evident. Striæ lineate, with coarser lines near the middle.

Not common. Port Penn, Delaware River.

Pl. 14, Fig. 4.

AMPHIPRORA ORNATA BAIL.

Frustule membranaceous, constricted in the middle, with well-marked folds extending from the junction line in both directions. Valve lanceolate, constricted in the middle and with protracted ends. Keel undulate on the edge.

A beautiful, transparent and delicate form, the only fresh-water species in our locality.

Delaware Water Gap, Pa.

Pl. 14, Figs. 6 and 7.

AMPHIPRORA PALUDOSA WM. SM.

Frustule membranaceous, constricted, with truncate ends. Valve linear, with acute ends. Striæ scarcely visible.

Cape May (Cleve).

Pl. 14, Fig. 5.

TROPIDONEIS CLEVE (1891)

(tropis, a keel)

Frustule oblong, constricted in the middle; keel not sigmoid. Axial area not evident. Striæ very fine, punctate, in longitudinal lines.

{69}TROPIDONEIS LEPIDOPTERA (GREG.) CLEVE

Valve with straight, median excentric line. Keel unilateral, projecting above the median line in zone view; central area small. Transverse striæ finely punctate. As usually seen, the valve is inclined. According to Karsten there are two chromatophores on the connective zone, each divided into four parts, each of which contains a large oval pyrenoid.

Amphiprora lepidoptera Greg.

Along the coast.

Pl. 14, Figs. 8 and 9.

AURICULA CASTRACANE (1873)

(auricula, the ear, the shape of the valve)

Frustule globose. Valve reniform or cymbiform, elevated into a keel which is not sigmoid. Median line biarcuate. Differs from Amphiprora in not having a sigmoid keel.

AURICULA MUCRONATA (H. L. SMITH) PERAGALLO

In zone view, the median line deeply bisects the longitudinal axis, ending in a mucronate central nodule. Connective zone complex. Valve very complex, with ventral margin nearly straight and raphe excentric. Central nodule near the margin, terminal nodules small. Striæ, 35-40 in 10 µ (Cleve). Chromatophore single, on the ventral part.

Amphora mucronata H. L. Smith.

Amphora (?) insecta Grun.

Auricula insecta (Grun.) Cleve.

"A rare and very curious pelagic species" (Peragallo, Diat. Villefranche).

Prof. H. L. Smith included this form in his first century of "Species Typicæ Diatomacearum," which was issued prior to 1876, the date of publication, in Schmidt's Atlas, of Amphora insecta Grun.

Atlantic City, N. J. Rare.

Pl. 15, Fig. 2.

SCOLIOTROPIS CLEVE (1894)

(scolios, twisted, and tropis, a keel)

Frustule linear, oblong. Median line sigmoid near the ends. Valve with transverse costæ alternating with two intermediate rows of puncta in oblique lines.

SCOLIOTROPIS LATESTRIATA VAR. AMPHORA CLEVE

Valve asymmetrical, with the median line curved. Frustule sub-acute at the ends. Median lines not on the same side of each valve of the frustule.

Abundant at Cape May, N. J. Not common elsewhere.

Pl. 14, Figs. 10 and 11.

GOMPHONEIS CLEVE (1894)

(gomphos, a peg, and neis (naus))

Valve elongated, asymmetrical to the transverse axis; axial area narrow; central area rounded, stigmatic; striæ radiating, costæ alternating with double rows of fine puncta. An indistinct, longitudinal line near the border.

Chromatophores and conjugation have not been determined.

{70}GOMPHONEIS HERCULANEUM (EHR.) CL.

Valve clavate, with rounded apex; costæ, 13 in 10 µ, alternating with double rows of fine puncta, 22 in 10 µ, in oblique rows; axial area narrow, central area rounded, with one stigma.

Gomphonema capitatum Ehr var. herculaneum Ehr., H. L. S., Type Slide No. 177.

Common in the blue clay.

Pl. 19, Fig. 2.

Pl. 38, Fig. 15, zone view of young frustule.

GOMPHONEIS MAMILLA (EHR.) CL.

Valve lanceolate, with rounded apex and base; striæ costate, 10 in 10 µ, alternating with double rows of fine puncta; axial area linear, sometimes oblique, central area small, with one or more stigmas.

Blue clay. Rare.

Pl. 19, Fig. 1.

In one frustule I noticed one valve with one stigma and the other with four stigmas.

The difference between G. mamilla and G. elegans is not very great. In the latter the central area is larger and the longitudinal lines not so near to the margin. The stigmas form a circlet. There appears to be a coincidence in the relation of Gomphoneis to Gomphonema, and that of the true Achnanthes to the group described by Cleve under Achnanthidium. In Gomphoneis and Achnanthes the striation is both costate and punctate while in Gomphonema and Achnanthidium the striation is punctate only.

GOMPHONEMA AG. (1824)

(gomphos, a peg, and nema, a filament)

Valve elongated, asymmetrical with respect to the transverse axis; striæ transverse, usually radiate, punctate.

Chromatophore band single, the middle lying on one zone.

In conjugation, according to Thwaites and Pfitzer, from two mother cells, which do not form a positive union, two auxospores are developed parallel to the original frustules. In Plate 19, Fig. 19, I have drawn a representation of the auxospore formation as I have frequently observed it in a gathering sent me by Mr. T. C. Palmer, containing G. angustatum, a common species in this locality. The sagittal plane of the valve of the auxospore is at right angles to the plane of the valve of the mother cell. Two valves of one of the mother cells are seen separated, one on each side of the auxospore which is nearly twice the length of the original frustules. The two valves of the other mother cell are not shown as they are not usually found closely united. In the figure one valve alone of the auxospore is seen, the opposite valve not being in focus. The valves of the auxospore are usually more or less arcuate, as in Cymbella, to which the genus is closely allied.

Grunow divides Gomphonema into two groups, Asymmetricæ and Symmetricæ, according to the presence or absence of stigmas. Cleve suggests Stigmaticæ and Astigmaticæ as more suitable in order to agree with the Cymbellæ. The Stigmaticæ are found chiefly in fresh water, sometimes in brackish. All of the marine forms belong to the Astigmaticæ, which, however, include some common fresh-water forms. Many species of Gomphonema are stipitate, some occur in gelatinous masses, and others are free.

{71}GOMPHONEMA MONTANUM SCHUM.

Valve slightly biconstricted, with obtuse apex and basis, somewhat cuneate; axial area linear, widened in the middle unilaterally; stigma, one; striæ about 11 in 10 µ, more distant in the middle, punctate.

Gomphonema subclavatum var. montana (Schum.) Cl.

Pavonia, N. J., artesian well. Rare.

Pl. 19, Fig. 3.

GOMPHONEMA GEMINATUM LYNG.

Valve biconstricted, with large, rounded, sub-truncate apex and broad, sub-truncate basis; striæ, 9 in 10 µ, radiate in the middle, alternately longer and shorter, transverse at the basis and near the apex where they again radiate, coarsely punctate, puncta, 12 in 10 µ. Axial area linear; central area rounded, with several large stigmas in a longitudinal row; terminal fissures hook-shaped.

Blue clay.

Pl. 19, Fig. 4.

GOMPHONEMA LANCEOLATUM VAR. INSIGNIS (GREG.) CL.

Valve lanceolate; axial area narrow; central area unilateral with one stigma; striæ with coarse and distant puncta.

Common and variable.

Gomphonema insigne Greg.

Pl. 19, Figs. 6 and 12.

Fig. 12 shows a unilateral central area. Fig. 6 is more clavate in outline with small central area. In both forms the coarse puncta are in distinct longitudinal lines in the middle.

GOMPHONEMA ACUMINATUM VAR. TURRIS (EHR.) CL.?

Valve clavate, with cuneate, acute apex; axial area distinct; central area unilateral with one stigma.

Blue clay.

Pl. 19, Fig. 11.

GOMPHONEMA ACUMINATUM VAR. TURRIS (EHR.) CL.

Valve clavate, with cuneate apiculate apex and narrow basis; axial area narrow, with a unilateral central space; stigma opposite the short striæ; striæ more radiate in the upper part, distant in the middle.

Smith's Island, Delaware River.

Pl. 19, Fig. 5.

GOMPHONEMA ACUMINATUM VAR. CORONATA (EHR.) CL.

Valve twice constricted, with broad, cuneate apex; striæ radiate in the middle, convergent near the apex and radiate at the apex. Variable in size and outline.

Blue clay. Fresh water. Common.

Pl. 19, Fig. 7.

GOMPHONEMA ACUMINATUM VAR. TRIGONOCEPHALA (EHR.) CL.

Valve broad, with cuneate apex; axial area narrow; central area unilateral with one stigma.

Pavonia, N. J., artesian well.

Pl. 19, Fig. 20.

{72}GOMPHONEMA CONSTRICTUM EHR.

Valve clavate, constricted beneath the abruptly rounded apex, gibbous in the middle, striæ alternately longer and shorter; axial area narrow, central area unilateral, with one stigma.

Common in fresh water.

Pl. 19, Fig. 8.

GOMPHONEMA SPHÆROPHORUM EHR.

Valve clavate, with capitate or rostrate-capitate apex and narrow basis; axial area very narrow; central area small, unilateral, with one stigma.

Common in fresh water.

Pl. 19, Figs. 9 and 10. Fig. 10 appears to be a transitional form having a more distinct axial area and rostrate apex.

GOMPHONEMA AUGUR EHR.

Valve broadly clavate, truncate and apiculate at the apex; basis sub-acute; axial area distinct; central area small, unilateral with one stigma; striæ with distant puncta.

Blue clay. Willistown, Pa.

Pl. 19, Fig. 21.

GOMPHONEMA INTRICATUM KUETZ.

Valve narrow, lanceolate, slightly gibbous in the middle; axial area distinct; central area transverse with one stigma; striæ parallel. Quite variable.

Common in fresh water.

Pl. 19, Fig. 14.

GOMPHONEMA ANGUSTATUM KUETZ.

Valve lanceolate, with sub-rostrate apex and basis; axial area indistinct; central area unilateral, with one small stigma; striæ slightly radiate, indistinctly punctate.

Very common in fresh water.

Pl. 19, Figs. 18 and 19.

Fig. 19, as stated above, represents the formation of an auxospore.

GOMPHONEMA ÆQUALE GREG.

Valve linear-lanceolate, nearly symmetrical, with capitate apex and basis; axial area narrow; central area unilateral, with one stigma; striæ radiate in the middle, slightly convergent at the ends.

Gomphonema intricatum var. æquale (Greg.) Cl.

Blue clay. Not common.

Pl. 19, Fig. 15.

GOMPHONEMA SARCOPHAGUS GREG.

Valve linear, irregular in outline, with rounded apex and basis; axial area distinct; central area small, unilateral, with one stigma; striæ irregular with coarse, distinct puncta.

Occasional in fresh water.

Pl. 19, Fig. 16.

GOMPHONEMA CAPITATUM EHR.

Valve clavate, broad at the sub-truncate apex and slightly constricted, or with parallel margins; axial area linear, central area stellate, with one stigma; striæ in the middle alternately longer and shorter.

Blue clay.

Pl. 19, Fig. 22.

{73}GOMPHONEMA PARVULUM VAR. MICROPUS (KUETZ.) CL.

Valve clavate, with rounded apex and basis; axial area indistinct; central area unilateral, with a small stigma; striæ distant in the middle.

Common.

Pl. 19, Fig. 17.

GOMPHONEMA VENTRICOSUM GREG.

Valve clavate, with broad apex and produced, rounded basis; axial area narrow, widened in the middle; stigma one; striæ distant in the middle, finely punctate.

Blue clay.

Pl. 19, Fig. 13.

GOMPHONEMA OLIVACEUM LYNG.

Valve clavate, with broad apex and narrow basis; axial area very narrow; central area irregular, without stigma; striæ radiate, finely punctate.

Very common.

Pl. 19, Fig. 23.

GOMPHONEMA BRASILIENSE VAR. DEMERARÆ GRUN.?

Valve lanceolate, with sub-cuneate apex and narrowed basis; axial area lanceolate, broad; no stigma; median fissures remote; striæ parallel, 12 in 10 µ, punctate, the puncta obsolescent, small or interrupted.

Willistown, Pa. Rare.

Pl. 19, Fig. 24.

PLEUROSIGMA WM. SM. (1852)

(pleura, a side, and sigma, the letter s)

Valve lanceolate, sigmoid; axial area very narrow, central area small; striæ punctate, in transverse and oblique lines.

Cleve divides the forms usually known as Pleurosigma into two genera, Pleurosigma and Gyrosigma. Pleurosigma includes all forms having oblique rows of puncta, while Gyrosigma includes all having longitudinal rows. Both have transverse striæ. The former consists entirely of marine species, while in the latter the species are found in fresh, brackish and salt water.

The endochrome in Pleurosigma, according to Mueller, consists of two bands which differ in the median part of each valve. Mereschkowsky says that the endochrome is so divided as to form four bands, two on each valve, that their position is different in different species, and that they are not the same on valves of the same frustule.

Cleve prefers to classify the species of Pleurosigma and Gyrosigma in accordance with the outline of the valve and the flexure of the median line. I shall, however, retain the method used by Peragallo and Grunow and arrange the forms according to the striation.

(1) OBLIQUE STRIÆ ABOUT 90 DEGREES, MORE DISTINCT THAN THE TRANSVERSE

PLEUROSIGMA FORMOSUM WM. SM.

Valve elongated, slender, gently sigmoid, acute at the ends; oblique striæ crossing each other at about 90 degrees; 10-16 in 10 µ; transverse striæ, 14-20 in 10 µ (Cleve).

Along the coast.

Pl. 22, Fig. 5.

{74}PLEUROSIGMA OBSCURUM WM. SM.

Valve linear, not sigmoid, or scarcely so; ends obtuse, subconical; raphe sigmoid, near the margin at the extremities; transverse and oblique striæ equidistant, 28 in 10 µ (Wm. Sm.).

Abundant at Greenwich Point, Philadelphia.

Pl. 22, Fig. 4.

(2) OBLIQUE STRIÆ CLOSER AT THE ENDS

PLEUROSIGMA NAVICULACEUM BRÉB.

Valve lanceolate, slightly sigmoid at the extremities; raphe strongly sigmoid near the margin at the ends; central nodule large, rounded; oblique striæ, 13-14 in the middle, closer at the ends; transverse striæ, 18-20 in 10 µ (Peragallo).

Long Island Sound.

Pl. 22, Fig. 6.

PLEUROSIGMA VIRGINIACUM H. L. SMITH

Valve slightly sigmoid, with acute ends; raphe more sigmoid than the valve, excentric near the ends; oblique striæ in different directions at the centre, 13 in 10 µ, closer and less distinct at the ends; central nodule small but prominent because of its thickness, producing by diffraction an apparently wide area (somewhat exaggerated in the figure). L. 95 µ, usually larger.

P. affine var. fossilis Grun. (Peragallo).

P. normanii var. fossilis Grun. (Cleve).

Common in the blue clay.

Pl. 22, Fig. 8.

(3) OBLIQUE STRIÆ 60 DEGREES

PLEUROSIGMA ANGULATUM (QUEKETT) CL.

Valve rhomboidal, with sub-rostrate or produced ends; central nodule rhomboidal; raphe central; transverse and oblique striæ at an angle of 60 degrees, equidistant, 18-22 in 10 µ.

Navicula angulata Quekett.

Along the coast.

Pl. 22, Fig. 3.

PLEUROSIGMA STRIGOSUM WM. SM.

Valve lanceolate, with sub-acute, somewhat revolute, apices; oblique striæ at an angle of about 60 degrees, otherwise as in angulatum.

Along the coast. Not common.

Pl. 22, Fig. 1.

PLEUROSIGMA ÆSTUARII BRÉB.

Valve lanceolate, with produced apices; raphe less sigmoid than the valve and excentric; oblique striæ, 19-21 in 10 µ, at an angle of about 60 degrees.

Along the coast. Common.

Pl. 22, Fig. 7.

{75}(4) OBLIQUE STRIÆ 60 DEGREES, THE TRANSVERSE MORE DISTANT

PLEUROSIGMA RIGIDUM WM. SM.

Valve nearly straight or slightly sigmoid, with obtuse ends; raphe central, excentric near the ends; oblique striæ, 17-21, transverse, 16-19 in 10 µ. (Peragallo).

New Rochelle, N. Y.

Pl. 22, Fig. 2 (very near the var. gigantea Grun.)

GYROSIGMA HASSALL (1845)

(gyros, curved, and sigma)

Valve lanceolate, sigmoid; axial area very narrow, central area small; striæ punctate, in transverse and longitudinal rows.

Chromatophores two, in long and narrow bands, perforated, differing from those of Pleurosigma. The elæoplasts are also arranged differently in the two genera. (Mereschkowsky, Études sur l'Endochrome des Diatomées, Imperial Academy of Petrograd, 1901, Vol. 11, No. 6, p. 18 et seq.)

The arrangement is according to Peragallo.

(1) LONGITUDINAL STRIÆ MORE DISTANT THAN THE TRANSVERSE

GYROSIGMA HIPPOCAMPUS (EHR.)

Valve lanceolate, sigmoid, with obtuse ends; raphe nearly central; transverse striæ 15-17, longitudinal, 10-12 in 10 µ.

Navicula hippocampus Ehr.

Pleurosigma hippocampus (Ehr.) Wm. Sm.

Gyrosigma attenuatum (Kuetz.) Cl.

Long Island Sound.

Pl. 23, Fig. 3.

(2) LONGITUDINAL AND TRANSVERSE STRIÆ NEARLY EQUAL

GYROSIGMA BALTICUM (EHR.) CL.

Valve with margins parallel nearly to the extremities, which are suddenly unilaterally sub-conical and obtuse; raphe sigmoid; transverse and longitudinal striæ nearly equally distant, 15 in 10 µ (Per.). L. 200-360 µ.

Navicula baltica Ehr.

Pleurosigma balticum (Ehr.) Wm. Sm.

Common along the coast.

Pl. 23, Fig. 2.

GYROSIGMA PARKERI VAR. STAURONEIOIDES GRUN.

Valve lanceolate, slightly sigmoid, ends produced into beaks with sub-acute apices; raphe straight in the middle part; central nodule elliptical; transverse striæ, 21, and longitudinal, 24 in 10 µ (Per.).

An apparent stauros, variable in width, extends to the margin and, in consequence, the median transverse striæ are more evident. L. 75 µ.

Schuylkill River. Rather rare.

Pl. 23, Fig. 7.

{76}GYROSIGMA SIMILE (GRUN.)

Valve slightly sigmoid, broad, with obtuse ends; raphe sigmoid, nearly central; transverse striæ, 15, longitudinal, 16-17 in 10 µ (Per.).

Pleurosigma simile Grun.

Gyrosigma balticum var. similis (Grun.) Cl.

Shark River, N. J.

Pl. 23, Fig. 4.

(3) TRANSVERSE STRIÆ MORE DISTANT

GYROSIGMA ACUMINATUM (KUETZ.) CL.

Valve sigmoid, tapering to the sub-acute ends; raphe central; transverse and longitudinal striæ nearly equally distant, 17 or 18 in 10 µ (Per.).

Frustulia acuminata Kuetz.

Port Penn, Delaware River.

Pl. 23, Fig. 5.

GYROSIGMA STRIGILIS (WM. SM.) CL.

Valve sigmoid, with obtuse ends; raphe doubly sigmoid; axial area rather wide; transverse striæ, 13, and longitudinal, about 16 in 10 µ.

Long Island Sound. Not common.

Pl. 23, Fig. 1.

GYROSIGMA KUETZINGII (GRUN.) CL.

Valve sigmoid, lanceolate, with sub-acute ends; raphe central, the central nodule elliptical; transverse striæ, 21-23, and longitudinal, 25-26 in 10 µ.

Pleurosigma spencerii var. acutiuscula Grun.

Pleurosigma spencerii var. kuetzingii Grun.

Common in fresh water.

Pl. 38, Fig. 12.

GYROSIGMA SCALPROIDES (RAB.) CL.

Valve slightly sigmoid, with obtuse ends; raphe nearly straight; central nodule elliptical; transverse striæ, 22, slightly radiate and more distant in the middle; longitudinal striæ, 29 in 10 µ. L. 60 µ.

Common in streams.

Pl. 38, Fig. 9.

In Pl. 23, Fig. 6 represents a form more sigmoid.

GYROSIGMA SPENCERII VAR. NODIFERA GRUN.

Valve sigmoid, with obtuse ends; raphe central; central nodule obliquely elongated; transverse striæ, 17-18 in 10 µ, curved in the middle of the valve, longitudinal striæ, 22 in 10 µ. L. 150 µ.

Blue clay.

Pl. 23, Fig. 8.

GYROSIGMA PROLONGATUM (WM. SM.) CL.

Valve narrow, lanceolate, produced into beaks, curved in a contrary direction; raphe central; transverse striæ, 20-21 in 10 µ, longitudinal closer. L. 140 µ.

Along the coast, northward.

Pl. 38, Fig. 13.

I have not seen any specimens south of New England, but they will probably occur.

{77}(4) STRIÆ ALIKE, EXTREMITIES PRODUCED

GYROSIGMA FASCIOLA (EHR.) CL.

Valve lanceolate, attenuated into curved beaks turned in opposite directions; raphe central, straight, except at the beaks; transverse striæ, 22, longitudinal, 24 in 10 µ (Per.).

New York Bay.

Pl. 23, Fig. 9.

FRUSTULIA AG. (1824); em. GRUN. (1865)

(frustulum, a small piece)

Valves naviculoid, similar, usually free but sometimes enclosed in gelatinous tubes or embedded in mucus. Median line between two thickened ribs. Central and terminal nodules frequently elongated. Surface of valve with fine puncta in longitudinal and transverse lines appearing hyaline under medium powers.

Chromatophores, two, extending along the girdle. They differ from those of Navicula in being separated from the wall in the middle by a hemispherical mass of protoplasm. According to Pfitzer, each chromatophore is divided in the middle, allowing a connection between the hemispherical mass and the central plasma mass. Schmitz states that the chromatophore is thickened in the middle and contains a pyrenoid.

In conjugation, two frustules form two cylindrical bodies which later become conical and from which are formed the sporangial valves twice the usual size.

FRUSTULIA LEWISIANA (GREV.) DE TONI

Valve elliptical or linear, with rounded ends; terminal nodules elongated, at a distance from the ends; striæ, 24 in 10 µ.

Port Penn, Delaware River. Along the coast.

Pl. 17, Fig. 1.

FRUSTULIA RHOMBOIDES (EHR.) DE TONI

Valve lanceolate or rhombic-lanceolate, rounded at the ends; central and terminal nodules short; striæ, 20 in 10 µ, sometimes coarser.

Common in fresh water.

Pl. 17, Fig. 2.

FRUSTULIA RHOMBOIDES VAR. AMPHIPLEUROIDES GRUN.

Valve rhombic-lanceolate; central and terminal nodules elongated; median line somewhat excentric.

Blue clay.

Pl. 17, Fig. 3.

FRUSTULIA RHOMBOIDES VAR. SAXONICA (RAB.) DE TONI

Valve smaller than in rhomboides, with somewhat produced ends, closer median ribs and rounded central nodule.

Fresh water.

Pl. 17, Fig. 6.

FRUSTULIA VULGARIS (THWAITES) DE TONI

Valve elliptical-lanceolate, with rounded or sometimes sub-rostrate ends; central and terminal nodules slightly elongated; striæ delicate, closer at the ends. Frustules at first in gelatinous tubes.

Colletonema vulgaris Thwaites.

Fresh water.

Pl. 17, Fig. 4.

{78}FRUSTULIA INTERPOSITA (LEWIS) DE TONI

Valve linear-elliptical, rounded at the ends; terminal nodules short.

Navicula interposita Lewis.

Along the coast. Port Penn, Delaware River.

Pl. 17, Fig. 5.

AMPHIPLEURA KUETZ. (1844)

(amphi, on both sides, pleura, a side)

Frustules free, in gelatinous masses or in tubes. Valve linear-lanceolate; central nodule narrow, extending half the length of the valve or more, then forking toward the ends. Terminal nodules prolonged, as in Frustulia, into a "porte-crayon-shaped" figure.

Chromatophores two, very short.

AMPHIPLEURA PELLUCIDA KUETZ.

Frustules free or in mucous masses. Valve fusiform; forks about one-fourth the length of the valve; striæ transverse, punctate, 36-40 in 10 µ (J. J. Woodward).

Occasional in the Delaware River.

Pl. 17, Fig. 9.

AMPHIPLEURA RUTILANS (TRENTEPOHL) CL.

Frustules enclosed in gelatinous tubes. Valve linear-lanceolate, obtuse at the ends; forks about one-third the length of the valve; striæ, 28 in 10 µ.

Conferva rutilans Trentepohl.

Schizonema dillwynii Wm. Sm.

Abundant at Belmar, N. J.

Pl. 17, Fig. 10.

Fig. 11 represents a portion of the gelatinous tube containing frustules.

DICTYONEIS CLEVE (1890)

(dictyon, a net)

Frustules oblong. Valve lanceolate, constricted in the middle (in our species); an outer layer finely punctate and an inner layer of reticulations; the margin of the valve divided into large, quadrate cells.

The genus Dictyoneis includes species at one time ascribed to Mastogloia and Navicula. The structure, however, is not like that of either, as the loculi are attached to the valve and are not separable as in Mastogloia, and the cell-wall is not like that of any Navicula.

Cleve remarks that Dictyoneis is found in warm waters. Lewis found one specimen at Black Rock Harbor, L. I., and one in the Delaware River blue clay. The specimens here described I found living on the New Jersey coast.

DICTYONEIS MARGINATA VAR. TYPICA CLEVE

Valve panduriform, with cuneate lobes; axial area narrow, linear, scarcely, or not at all, widened in the middle; terminal fissures in contrary directions; outer stratum finely punctate, about 25 in 10 µ, in parallel striæ; inner stratum coarsely reticulated. Four and one-fourth times longer than broad; marginal cells, 5 in 10 µ, smaller or obsolescent in the middle of the valve; cells of the valve in irregular transverse rows, 10-12 in 10 µ. L. 93 µ.

Navicula marginata Lewis.

Absecon, N. J.

Pl. 20, Fig. 3.

{79}DICTYONEIS MARGINATA VAR. COMMUTATA CLEVE

Valve four and one-half times longer than broad; cells of the valve in irregular, transverse rows about 11 in 10 µ; marginal cells nearly equal, 6 in 10 µ. L. 125 µ.

Absecon, N. J.

Pl. 20, Fig. 2.

DICTYONEIS MARGINATA VAR. MAXIMA N. VAR.

Valve with cuneate segments; marginal cells, 4 in 10 µ; cells of the valve, 5 in 10 µ, obsolescent in the middle and smaller; transverse striæ, 25 in 10 µ.

Atlantic Coast. Rare.

Pl. 20, Fig. 1 (from a specimen found at Colon).

TRACHYNEIS CLEVE (1894)

(trachys, rough, and neis (naus), named from the chief species)

Valve more or less linear or linear-lanceolate. It appears to be composed of three strata, one an interior, coarsely dotted, an exterior of fine puncta in longitudinal striæ, scarcely visible, and a median of transverse anastomosing costæ forming irregular alveoli.

Chromatophores, two or four bands on the zone (Mereschkowsky).

TRACHYNEIS ASPERA VAR. INTERMEDIA GRUN.

Valve linear-elliptic; axial area a stauros widened outward and unilateral. Striæ of the median layer of radiating rows of oblong alveoli.

Along the coast. Not common.

Pl. 17, Fig. 15.

The type form and its numerous varieties are quite ubiquitous. Very large specimens occur in the Antarctic regions, especially in material from Ross Island, S. Victoria Land (Shackleton Ant. Exp.).

BRÉBISSONIA GRUN. (1860)

(named after Alphonse de Brébisson, the distinguished French naturalist)

Frustules stipitate; valve lanceolate; striæ transverse in the middle, radiate at the ends. Median area narrow, central nodule elongated, terminal fissures at a distance from the ends. Valve with an outer finely punctate stratum.

At one end of one valve in each frustule is found a conspicuous punctum, the plasma pore of Otto Mueller, through which the frustule is connected with the gelatinous stipe, analogous to the pore in Diatoma connecting the zig-zag frustules.

Chromatophore single, lying on one girdle and passing over to each valve.

BRÉBISSONIA BOECKII (KUETZ.) GRUN.

Valve lanceolate, with sub-acute apices; striæ, 3-4 in 10 µ, not reaching the median line.

Blue clay. Very rare. Common in brackish water at Chestertown, Md. (T. C. Palmer)

Pl. 17, Fig. 7.

{80}BRÉBISSONIA PALMERII, N. SP.

Valve rhombic-lanceolate, with cuneate ends and produced apices. Central nodule more elongate and terminal fissures further from the ends than in B. boeckii.

Pavonia, N. J. (artesian well, depth of 40 ft.). Rare.

Pl. 17, Fig. 8.

I take pleasure in naming this species after Mr. T. Chalkley Palmer, of Media, Pa., the author of numerous papers on the Diatomaceæ.

Lewis partly describes a similar form, which he does not name, as a species of Navicula found in the blue clay at Kaighn's Point, N. J. (Lewis, "New and Intermediate Forms," etc., p. 15, Pl. 1, Fig. 8.)

ANOMOEONEIS PFITZER (1871)

(anomoios, unlike, and neis (naus), a boat)

Valve lanceolate, axial area narrow, central area widened; transverse striæ punctate, the puncta in longitudinal rows or interrupted by blank lines.

A single chromatophore lies along one of the girdle sides and extends over the valves, each of the two parts being deeply notched or slit at the ends. According to Schmitz there are two pyrenoids, but Heinzerling thinks there is but one.

Cleve considers this genus not well founded, as it is based upon the cell contents of but one species, the structure of the other species not being known. As the forms here described are easily recognized by the interrupted puncta, the genus is, at least, convenient.

ANOMOEONEIS SPHÆROPHORA (KUETZ.) CL.

Valve elliptic-lanceolate, ends rostrate-capitate. Axial area narrow, central area rounded, larger on one side of the median line than the other. Striæ very slightly radiate, 16 in 10 µ, punctate, the puncta interrupted by longitudinal blank lines.

Pfitzer states that the central plasma mass is unequal on the two sides.

Navicula sphærophora Kuetz.

Fresh and brackish water. Not common.

Pl. 40, Fig. 2.

ANOMOEONEIS SERIANS (BRÉB.) CL.

Valve lanceolate, acute; axial area lanceolate; striæ, 24 in 10 µ; puncta elongate.

Not common in this locality, but abundant northwards; fossil in the peat deposits of New England.

May's Landing, N. J.

Pl. 17, Fig. 12.

Forma minor--Valve rhombic-lanceolate, smaller than the type.

May's Landing, N. J.

Pl. 17, Fig. 13.

ANOMOEONEIS FOLLIS (EHR.) CL.

Valve rhomboid, tumid in the middle and obtuse at the produced ends. Central area lanceolate; striæ radiate in the middle, transverse at the ends.

Navicula follis Ehr.

Navicula trochus Kuetz.

{81}Reported by Lewis as very rare in the blue clay of the Delaware River. I have not seen it in this locality. The figure is drawn from a specimen in the W. Bridgewater, Mass., deposit.

Pl. 17, Fig. 14.

CALONEIS CLEVE (1894)

(calos, beautiful)

Valve convex, linear or lanceolate in general outline, with transverse, smooth or finely punctate striæ crossed by one or more longitudinal lines.

Endochrome of two chromatophores lying one on each valve, entire in some species and deeply cleft in others.

CALONEIS LIBER (WM. SM.) CL.

Valve linear, with parallel margins and rounded ends; axial area narrow, central area orbicular; striæ transverse in the middle, slightly divergent at the ends, 16 in 10 µ; terminal fissures slightly curved in the same direction; longitudinal line median. L. 82 µ.

Atlantic coast, chiefly southward.

Pl. 40, Fig. 1.

CALONEIS SILICULA (EHR.) CL.

Valve linear, gibbous in the middle, with broad sub-cuneate ends; axial area narrow, central area rounded; longitudinal line marginal; striæ parallel or nearly so, 16 to 18 in 10 µ.

Navicula silicula Ehr.

Navicula limosa Donk.

Blue clay.

Pl. 21, Fig. 3 (var. genuina Cl.).

CALONEIS SILICULA VAR. INFLATA (GRUN.) CL.

Valve gibbous in the middle, with rounded ends; central area elliptical.

Schuylkill River.

Pl. 21, Fig. 4.

C. silicula may be recognized by its yellow color when dry. Its varieties are extremely numerous.

CALONEIS TRINODIS (LEWIS)

Valve divided into three segments of equal width; ends cuneate and usually produced; axial area elliptical with a lunate marking on each side; striæ radiate in the middle, elsewhere parallel, about 20 in 10 µ, finely punctate; longitudinal line marginal, scarcely visible; the striæ become fainter toward the axial area.

Occasional in streams and in the blue clay. Abundant in a water-trough at Ashbourne, Pa.

Pl. 21, Fig. 8.

I have retained Lewis' name as specific. Lewis, wrongly, I think, ascribes his species to Navicula trinodis Wm. Sm., which is not figured by Smith, but is illustrated by Van Heurck (Syn. Pl. 14, Fig. 31a), and is named by Cleve Navicula contenta var. biceps Arnott. {82}De Toni includes Lewis' name under Rhoiconeis trinodis (Wm. Sm.) Grun. Rhoiconeis is achnanthiform, with frustules arcuate, and the species is named by Cleve Achnanthes trinodis (Arnott). Caloneis schumanniana (Grun.) Cl., to which as a variety Cleve unites Lewis' form, appears to resemble it only in the lunate marks.

Fig. 9 represents a single specimen found in the Pavonia deposit and which I believe to be an abnormal form of C. trinodis, differing only in the degree of inflation and in the larger central area.

Navicula trinodis var. inflata Schultze, from Staten Island, is the same form figured by Lewis, who states that certain specimens have produced apices.

CALONEIS PERMAGNA (BAIL.) CL.

Valve lanceolate, with produced apices; median line nearly straight; axial area lanceolate, irregular or slightly unilateral, about half the width of the valve; striæ, 9 in 10 µ, radiate and indistinctly punctate; longitudinal lines double. L. 100-200 µ.

Pinnularia permagna Bail.

Common in brackish water.

Pl. 21, Fig. 1.

CALONEIS PERMAGNA VAR. LEWISIANA N. VAR.

Valve lanceolate, with undulating sides and sub-cuneate apices; axial area less than one-third the width of the valve; striæ radiate, 12 in 10 µ, indistinctly punctate; longitudinal lines double, closer together than in the type. L. 140 µ.

Lewis illustrates this variety in "New and Rare Species," Pl. 2, Fig. 11, and states that it is probably Navicula esox Kuetzing. This is an error, as Kuetzing's species is Pinnularia esox Ehr., a form near P. major.

Rather common in the Delaware River.

Pl. 21, Fig. 2.

CALONEIS FORMOSA (GREG.) CL.

Valve lanceolate, with sub-cuneate apices; axial area one-fourth to one-fifth the width of the valve, somewhat unilateral, dilated in the middle; striæ, 12-14 in 10 µ radiate, punctate; longitudinal lines double, distinct. Variable in size and outline.

Abundant along the shores of the Delaware River.

Pl. 21, Fig. 18.

CALONEIS BREVIS VAR. VEXANS (GRUN.) CL.

Valve elliptical-lanceolate; apices obtuse; median fissures distant; axial area narrow; central area large, orbicular; longitudinal lines close together, median.

Shark River, N. J.

Pl. 21, Fig. 5.

CALONEIS WARDII CL.

Valve linear, ends cuneate; axial area linear; central area dilated to a stauros reaching the margin; striæ parallel, radiate at the ends, 18 in 10 µ; longitudinal lines marginal.

Not uncommon in the Delaware River.

Pl. 21, Figs. 6 and 7.

{83}CALONEIS POWELLII (LEWIS) CL.

Valve linear, with cuneate ends; axial area linear; central area large, quadrate, united to the wide longitudinal lines; striæ parallel, smooth, 8 in 10 µ.

Long Island (Lewis); Smith's Island, Delaware River.

Pl. 21, Fig. 10.

NEIDIUM PFITZER (1871)

(neidion, dim. of naus, a boat)

Valve linear or lanceolate; median fissures turned in opposite directions, terminal fissures appearing bifurcate (?); striæ transverse, usually oblique, finely punctate, crossed by one or several longitudinal blank lines.

Chromatophores, two, lying on the girdle side, in cell division each forming a partially divided pair. A large pyrenoid is said to be found in the middle of each chromatophore, but Mereschkowsky states that the pyrenoids are absent, but that in N. affine four elæoplasts are always seen in the centre of the frustule.

A genus easily recognized by the peculiar terminal and median fissures and by the yellowish or brownish color of the valves when dry, darker than in Caloneis.

NEIDIUM AFFINE (EHR.) PFITZER

Valve linear, with protracted, sub-rostrate or capitate ends.

Navicula affinis Ehr.

NEIDIUM AFFINE VAR. GENUINA FORMA MAXIMA CL.

Striæ, 14 in 10 µ, punctate, oblique in the middle, convergent at the ends; puncta, 15 in 10 µ. L. 238 µ.

Pensauken, N. J. (artesian well).

Pl. 21, Fig. 11.

Var. genuina forma minor Cl.--L. 26 µ; striæ, 24 in 10 µ.

Brandywine Creek.

Pl. 21, Fig. 12.

NEIDIUM AFFINE VAR. AMPHIRHYNCUS (EHR.) CL.

Valve linear, with protracted capitate ends; striæ transverse, interrupted by several longitudinal lines.

Willistown, Pa.

Pl. 21, Fig. 13.

NEIDIUM AMPHIGOMPHUS (EHR.) PFITZER

Valve with parallel margins and cuneate ends; striæ transverse, interrupted by several longitudinal lines; central area widened transversely.

Navicula amphigomphus Ehr.

Wissahickon.

Pl. 21, Fig. 14.

NEIDIUM PRODUCTUM (WM. SM.) CL.

Valve linear, elongate, with capitate apices; striæ slightly oblique; longitudinal lines marginal; axial area very narrow, central area small.

Navicula producta Wm. Sm.

Newtown Square.

Pl. 21, Fig. 16.

{84}NEIDIUM IRIDIS (EHR.) CL.

Valve linear or lanceolate-elliptical, with sub-cuneate or rounded ends; striæ oblique, about 18 in 10 µ; central area orbicular.

Navicula iridis Ehr.

Navicula firma Kuetz.

Willistown, Pa.; Middletown, Delaware Co., Pa. (Palmer).

Pl. 21, Fig. 17.

The form here figured is probably the variety ampliata (Ehr.) Cl. with less acute apices and more elliptical outline. The species occurs in many variations, the larger being found northward, especially in the peat deposits of New England.

NEIDIUM HITCHCOCKII (EHR.) CL.

Valve linear, with triundulate margin and cuneate ends; striæ transverse, oblique.

Navicula hitchcockii Ehr.

Pavonia, N. J. (artesian well); Kirkwood Pond, N. J.

Pl. 21, Fig. 15.

DIPLONEIS EHR. (1840)

(diplos, double)

Valve elliptical or panduriform; median line enclosed in strongly siliceous horns corresponding to the lyre-shaped areas of Navicula lyra but never punctate; central nodule, quadrate; valve costate, or striate, or both; between the horns and the outer part are thinner spaces or sulci, and, in some species, outside of the sulci are narrow spaces known as lunulæ.

Chromatophores, two, upon the girdle or the valves. Pyrenoids have been found in one species only, D. interrupta.

DIPLONEIS ELLIPTICA (KUETZ.) CL.

Valve elliptical; central nodule large; sulci narrow, curved, close to the horns; striæ punctate, in rows radiating more and more toward the ends. Variable in size and in the coarseness of puncta which are from 10 to 13 in 10 µ (Cleve).

Cleve describes D. ovalis Hilse as having the central nodule rounded, but otherwise about the same as D. elliptica, and as equivalent to Navicula ovalis A. Schmidt (Atlas, Pl. 7, Figs. 33 to 36).

Very common in fresh water and occasional in brackish.

Pl. 20, Fig. 14.

DIPLONEIS SMITHII (BRÉB.) CL.

Valve elliptical; central nodule not broad; furrows evenly curved on the outer edge, crossed by costæ and double oblique rows of alveoli. Variable in size and in the curvature of the furrows.

Cleve forms a new species, D. major, of the large form figured by Schmidt (Atlas, Pl. 7, Figs. 18, 19, 21 and 22), stating that the structure is much coarser and the form is larger with broad furrows. In the specimen here figured the size is median and the furrows are as in D. major.

Marine and brackish. Common.

Pl. 20, Fig. 17.

{85}DIPLONEIS CRABRO VAR. PANDURA (BRÉB.) CL.

Valve constricted, segments tongue-shaped; central nodule small; horns narrow, nearly parallel, with a row of large puncta; costæ, 4 in 10 µ, convergent in the middle, radiating at the ends, alternating with a double row of puncta, 11 in 10 µ.

Pavonia, N. J. (artesian well).

Pl. 20, Fig. 4.

DIPLONEIS CRABRO VAR. EXPLETA (A. S.) CL.

Valve slightly constricted, segments tongue-shaped; costæ robust, 5 or 6 in 10 µ, alternating with double rows of rather coarse puncta. L. 56 µ.

Port Penn, Delaware River.

Pl. 20, Fig. 15.

DIPLONEIS CRABRO VAR. PANDURELLA CL.?

Valve constricted, the lobes elliptical; central nodule large, with horns parallel in the middle, convergent at the ends; furrows wide, with faint costæ; no lunula; costæ parallel in the middle, radiate at the ends, 9 in 10 µ, alternating with very fine double rows of puncta (not shown in the figure). L. 65 µ.

Blue clay.

Pl. 20, Fig. 13.

DIPLONEIS CRABRO VAR.?

Valve constricted, segments elliptical; costæ, 8 in 10 µ, converging in the middle, radiating at the ends; horns narrow; furrows wide, costate; lunulæ indistinct. L. 75 µ.

Resembles var. pandurella except in the convergence of the costæ and in the lunula.

Squan River. Marine.

Pl. 20, Fig. 9.

DIPLONEIS FUSCA VAR. DELICATA (A. S.) CL.

Valve elliptical; furrows broad, crossed with rows of faint costæ and alveoli; costæ, 6 or 7 in 10 µ; alveoli, 10 in 10 µ, in short, irregular, longitudinal rows. L. 84 µ.

Port Penn, Delaware River.

Pl. 20, Fig. 11.

DIPLONEIS GRUENDLERI (A. S.) CL.

Valve constricted, segments tongue-shaped, often unequal; horns broad, divergent in the middle; furrows narrow; costæ transverse, crossed by from 3 to 7 longitudinal costæ, interrupted in the middle at the border.

Blue clay.

Pl. 20, Figs. 7 and 8.

DIPLONEIS PUELLA (SCHUM.) CL.

Valve elliptical, sometimes orbicular; furrows very narrow; striæ, 20 in 10 µ, indistinct. L. 15 µ.

Diploneis elliptica var. minutissima Grun.

Shark River, N. J. Brackish.

Pl. 20, Fig. 12.

DIPLONEIS EXCENTRICA, N. SP.

Valve elliptical; central nodule quadrate; furrows of the same width throughout, nearly parallel; costæ radiating toward the ends, 10 in 10 µ, indistinct on the furrows, alternating with alveoli, 7 in 10 µ, in irregular, longitudinal lines. One side of the valve is one and a half times the width of the other. L. 49 µ.

{86}I can find neither description nor figure of any species to which I can ascribe this form. It approaches D. elliptica. The alveoli are quite distinct and distant from each other.

Brackish water. Very abundant in a gathering from Squan River, N. J.

Pl. 20, Fig. 10.

DIPLONEIS OCULATA (BRÉB.) CL.

Valve elliptical; striæ radiate at the ends, about 20 in 10 µ, coarsely punctate. L. 23 µ.

Fresh water.

Pl. 26, Fig. 7.

The figure is drawn from Brébisson's original material in H. L. Smith's Type Slide No. 299.

Navicula oculata Bréb.

Reported from New Jersey. I have not seen this species in this locality. Navicula oculata, referred to by Kain as occurring in Shark River, is not this form.

DIPLONEIS GEMMATA (GREV.) CL.

Valve oblong-linear, with cuneate ends and parallel or slightly concave sides; central nodule large; horns parallel; furrows about one-third the width of the valve. Costæ about 5 in 10 µ, alternating with double rows of fine puncta; short costæ occur along the borders of the horns.

Port Penn, Delaware River.

Pl. 20, Fig. 16.

DIPLONEIS CAMPYLODISCUS (GRUN.) CL.

Valve suborbicular; central nodule quadrate; horns divergent; costæ, 6 in 10 µ, alternating with double rows of alveoli; furrows broad, costate near the horns.

Differs from Cleve's description in having 6, instead of 4, costæ in 10 µ.

Pensauken, N. J. (artesian well). Rare.

Pl. 20, Fig. 6.

MASTOGLOIA THWAITES (1856)

(mastos, a breast, and gloios, gelatinous, referring to the "mamillate cushion" in which the frustules are often immersed)

Frustule rectangular. Valves similar, naviculoid. Central and axial areas usually narrow or indistinct; striæ punctate, parallel in the middle. On each side, between the valve and the zone, is a septate plate.

ANALYSIS OF SPECIES

Striæ interrupted by a hyaline furrow on each side of the median line kinsmanii

Striæ not interrupted:

Loculi, five, or less exigua

more than five, equal, ending at distance from the ends smithii

ending near the ends, distinct lanceolata

indistinct elegans

very numerous apiculata

unequal angulata

{87}Karsten states that there are two chromatophores, each of which extends from the middle of one valve to the end and down the middle of the other valve. Mereschkowsky says, however, that there are four plates or chromatophores, sometimes on the valve, sometimes on the zone, according to the species, and that two long pyrenoids unite the two opposite chromatophores.

MASTOGLOIA KINSMANII LEWIS

Valve lanceolate-elliptical, with sub-rostrate ends; loculi more numerous than in M. angulata but less than in M. apiculata, the middle ones larger. Median line with a sulcus on each side; central area quadrate.

Mastogloia braunii Grun. (According to Cleve).

Atlantic City.

Pl. 17, Fig. 16.

MASTOGLOIA EXIGUA LEWIS

Valve elliptical- or linear-lanceolate; loculi, 2-5, usually 3, larger in the middle and rounded; central space small; striæ, 20-24 in 10 µ.

Along the coast.

Pl. 17, Fig. 24.

MASTOGLOIA SMITHII THWAITES

Valve lanceolate, sub-rostrate; loculi forming a wide band ending at a distance from the ends; striæ transverse, with puncta forming longitudinal rows; central area rounded or transversely elliptical.

Along the coast.

Pl. 17, Fig. 19.

MASTOGLOIA LANCEOLATA THWAITES

Valve lanceolate, with sub-rostrate apices; loculi very numerous; median and central areas indistinct; striæ, 19 in 10 µ, punctate, convergent at the ends.

Along the coast.

Pl. 17, Fig. 18.

MASTOGLOIA ELEGANS LEWIS

Valve lanceolate, acute; loculi indistinct or rudimentary, extending to the ends; central area apparently quadrate, sometimes indistinct; puncta distinct, 15 in 10 µ, in transverse and longitudinal rows.

Along the coast. Common.

Pl. 17, Fig. 20.

MASTOGLOIA APICULATA WM. SM.

Valve elliptical-lanceolate, sometimes with slightly produced apices; median line between two ribs; central space very small; loculi numerous; puncta in slightly radiating rows and in longitudinal lines.

Along the coast.

Pl. 17, Figs. 21, 22, 23.

MASTOGLOIA ANGULATA LEWIS

Valve elliptical, with produced apices; loculi usually less than 12, unequal, the larger in the middle; striæ, 12 in 10 µ, puncta in decussating rows. "Differs from apiculata in its more broadly elliptical shape, the smaller number of its loculi and the angular character of its striation" (Lewis).

{88}Considered by Cleve as synonymous with M. apiculata Grun., not Wm. Smith, and by De Toni as synonymous with M. apiculata Wm. Sm. In any case, M. angulata Lewis is not the same as M. apiculata Wm. Sm., the loculi of which are equal.

Atlantic City. H. L. Smith T. S. No. 211.

Pl. 17, Fig. 17.

STAURONEIS EHR. (1843)

(stauros, a cross, and neis (naus), a boat)

Frustules free, sometimes geminate; valve as in Navicula but with a stauros. Cell contents as in Navicula. Mereschkowsky, however, says that the chromatophores always contain more pyrenoids than are found in Navicula. Heinzerling gives the number as two to four in each chromatophore.

Cleve includes under Naviculæ Microstigmaticæ all species of Stauroneis, Pleurostauron, Schizostauron, certain Schizonemæ and Naviculæ. As a matter of convenience, and because I have already included certain Schizonemæ and Scoliopleura under Navicula, and because of the small number of species in our locality, I have arranged them under the three divisions of Cleve as follows:

Stauroneis.--Forms having a true stauros, without diaphragms.

Pleurostauron.--Forms like Stauroneis but with diaphragms at the ends.

Schizostauron.--Forms having a bifid stauros.

STAURONEIS PHOENICENTERON EHR.

Valve lanceolate, obtuse; striæ radiate, 18 in 10 µ, distinctly punctate. L. usually 125 µ but sometimes 200 µ.

Common in fresh water.

Pl. 27, Fig. 1.

STAURONEIS ANCEPS EHR.

Valve lanceolate, with rostrate or capitate ends; stauros in some cases does not reach the margin. The varieties are very numerous.

Var. gracilis (Ehr.) Cl.--Valve lanceolate, striæ very fine; margin of stauros striated. L. 100 µ. Cape May, N. J. Pl. 27, Fig. 5.

Var. amphicephala (Kuetz.) Cl.--Valve capitate at the ends; striæ, 24 in 10 µ. L. 47 µ. Fresh water. Pl. 27, Fig. 7.

Var. ?--Valve with produced ends; striæ, 30 or more in 10 µ. L. 104 µ. Willistown, Pa. Pl. 27, Fig. 4.

Var. ?--Valve with produced ends; striæ, about 28 in 10 µ, punctate. L. 47 µ. Newtown Square. Pl. 27, Fig. 8.

Var. ?--Valve with produced ends; striæ, 22 in 10 µ, showing a tendency to form longitudinal rows of puncta as in Stauroneis stodderi Greenleaf, but the rows are not so evident. L. 60 µ. Pavonia, N. J., artesian well. Pl. 27, Fig. 9.

STAURONEIS FRICKEI VAR. ANGUSTA N. VAR.

Valve lanceolate, gradually tapering to the obtuse ends; terminal fissures prominent, forking at a distance of 7 µ from the ends. Frustules frequently geminate. L. 173 µ.

Newtown Square. Rare.

Pl. 26, Fig. 18.

Near Stauroneis frickei A. S. (Atlas, Pl. 242, Fig. 16), except that the stauros is narrow at the margin.

{89}STAURONEIS SALINA WM. SM.

Valve lanceolate, obtuse; stauros narrow, with short, scattered striæ at the margin, 18 in 10 µ, punctate. L. 65 µ.

Along the coast. Common.

Pl. 27, Fig. 6.

STAURONEIS LEGUMEN EHR.

Valve elliptical-lanceolate, inflated in the middle, with produced sub-capitate or rostrate ends separated by diaphragms. Stauros wide, striated at the margins; axial area very narrow; striæ radiate, about 26 (?) in 10 µ, punctate. L. 28 µ.

Pavonia, N. J., artesian well.

Pl. 39, Fig. 15.

In Cleve's description and Van Heurck's figure, the median inflation is "not larger than the others." In the present form the median inflation is wider.

STAURONEIS ACUTA WM. SM.

Valve rhombic-lanceolate, obtuse; a diaphragm at each end; stauros widened outwards; striæ, 15 or 16 in 10 µ, punctate. L. 130 µ.

Blue clay.

Pl. 27, Fig. 2.

STAURONEIS AMERICANA A. S.

Valve elliptical-lanceolate, obtuse; striæ, 14 in 10 µ. L. 119 µ.

Pavonia, N. J., artesian well. Rare.

The only specimen found is asymmetrical with respect to the transverse axis.

On Plate 40, Fig. 4, is illustrated an abnormal form of Stauroneis, apparently near S. acuta, having an elongated central nodule and radiating, curved and coarsely punctate striæ. Blue clay.

STAURONEIS SMITHII GRUN.

Valve lanceolate, inflated in the middle and at the ends, which have diaphragms and are produced into rostrate apices; stauros reaching the margin; striæ parallel, about 25 in 10 µ (28 to 30, Cleve), distinctly punctate.

Not uncommon in meadow pools near Newtown Square.

Pl. 27, Fig. 11.

STAURONEIS CRUCICULA (GRUN.) CL.

Valve lanceolate, with obtuse, produced ends; stauros bifid; striæ, 24 in 10 µ, oblique, parallel to the branches of the stauros, closer at the ends, punctate. L. 32 µ.

Newtown Square. East Park Reservoir. Rare.

Pl. 27, Fig. 10.

NAVICULA BORY (1826)

(dim. of navis, a boat)

Valve linear to elliptical; ends acute, rounded, rostrate, capitate or truncate; axial area usually distinct; central area distinct, rounded or rarely extended into a transverse fascia; striæ transverse or radiate, punctate; central area not dilated into a transverse stauros nor into horns.

{90}The endochrome in the greater number of species consists of two chromatophores extending along the zone and sometimes partly over the valves. Sometimes, however, as in N. hennedyi, N. lyra and N. humerosa, the bands are on the valves. Certain species have four bands, others eight, and in one the endochrome is granular. (Mereschkowsky, l. c., p. 9 et seq.) Pyrenoids are usually absent. On account of the diversity of the chromatophores, Mereschkowsky considers the genus not homogeneous. The difficulty of arranging groups according to the cell contents, however, is so great that, for the present, the species must be described by the usual characteristics of the valves and divided as follows, according to Cleve, to the extent of employing the classification of all Naviculoid forms as applicable, especially to the species of Navicula. Van Heurck's analysis includes Pinnularia, Trachyneis, Diploneis, Caloneis, Neidium and Anomoeoneis, which are here separated, while N. lyra and N. hennedyi are placed in different groups, although they are closely related. In other respects Cleve's divisions correspond, to some extent, to those of Van Heurck.

The genus Navicula at one time included the following: Dictyoneis, Pleurosigma, Gyrosigma, Caloneis, Neidium, Diploneis, Frustulia, Trachyneis, Anomoeoneis, Pinnularia and Stauroneis, and few forms with a raphe escaped. For this reason the diagnosis of the present genus is somewhat limited. Pleurosigma and Gyrosigma differ from Navicula in their outline, Dictyoneis in the double stratification, Caloneis in the marginal lines, Neidium in the median and terminal fissures, Diploneis in the horns, Frustulia in the terminal nodules, Trachyneis in the stratification of the valve, Anomoeoneis in the longitudinal arrangement of the puncta, Pinnularia in the smooth costæ and Stauroneis in the stauros.

As the object of the present work is to aid the student of local forms in the identification of species by the briefest methods, the further discussion of the reasons for classification will be left for his gratification in referring to the authorities on the subject.

PUNCTATÆ CLEVE

Valve elliptical to lanceolate; central nodule not stauroid or continued into lyriform spaces; striæ distinctly or coarsely punctate, in radiate rows.

NAVICULA MACULATA (BAIL.) CL.

Valve lanceolate-elliptical, with produced or sub-rostrate ends; axial area narrow, wider near the ends and dilated to a rounded, transverse central area; striæ radiate, 6 in 10 µ, puncta, 7 in 10 µ, in irregular, longitudinal rows. L. 90 to 120 µ (Cl.).

Stauroneis maculata Bail.

Navicula fischeri A. S.

Blue clay. Along the coast, especially southward.

Pl. 24, Fig. 1.

NAVICULA LATISSIMA GREG.

Valve oblong-elliptical or elliptical-lanceolate, with sub-cuneate ends; axial area lanceolate, widened in the middle to an orbicular space; striæ radiate, 7 in 10 µ, puncta, 11 in 10 µ, the median striæ alternating with short striæ along the sides. L. 50-150 µ (Cl).

Blue clay. Pavonia, N. J., artesian well.

Pl. 24, Fig. 3.

{91}NAVICULA LATISSIMA VAR. ELONGATA (PANT.) CL.

Valve elliptical-lanceolate, with rounded ends; striæ and puncta closer than in the type form; axial area narrow, widened in the middle; terminal fissures hook-shaped, turned in different directions.

Navicula humerosa var. elongata Pant.

Fossil at Buckshutem, N. J.

Pl. 24, Fig. 5.

NAVICULA FUCHSII PANT.

Valve elliptical, with slightly produced apices; axial area wide, lanceolate; central area orbicular; striæ alternately longer and shorter in the middle, 10-12 in 10 µ; puncta on the border of the axial area larger, elongated; median fissures incrassate.

Navicula humerosa var. fuchsii (Pant.) Cl.

Navicula (latissima var.?) fuchsii Pant.

Port Penn, Delaware River.

Pl. 24, Fig. 6.

NAVICULA HUMEROSA BRÉB.

Valve lanceolate-elliptical or oblong-elliptical, with sub-cuneate or sub-rostrate ends; axial area narrow, lanceolate; central area rounded, somewhat transverse; terminal fissures hook-shaped, in the same direction; central pores incrassate; striæ, 11 in 10 µ, the middle alternately longer and shorter, closer at the ends. L. 60-86 µ. Variable in size, outline and fineness of striation.

N. monilifera Cleve (N. granulata Bréb.) differs in having coarser striæ.

Blue clay. Along the coast.

Pl. 25, Fig. 5.

NAVICULA PUSILLA WM. SM.

Valve ovate-elliptical, with rostrate or sub-rostrate ends; axial area narrow; central area elliptical; striæ radiate, 10-12 in 10 µ in the middle where they are longer and shorter alternately, closer at the ends; median fissures somewhat incrassate, terminal in the same direction. L. 47 µ.

Smith's Island, Delaware River.

Pl. 25, Figs. 4, 6?

Cleve gives the striæ as 13-18 in the typical form, and 11-13 in varieties. In the form here figured the striation is as stated by De Toni, but is about 19 at the ends.

Fig. 6 appears to be a small form of N. pusilla, near lanceolata Grun., at least according to the figure in "Arctic Diatoms," but not Gregory's figure. It occurs rarely in fresh water at Newtown Square. It may be a small form of N. punctulata and, if so, is probably accidental, as the material is entirely fresh-water.

NAVICULA PUSILLA VAR. SUBCAPITATA N. VAR.

Valve elliptical with rostrate-capitate and truncate ends; striæ about 12 in 10 µ in the middle where they are unequal; axial area narrow, slightly widened in the middle; central pores incrassate, terminal fissures in the same direction. Differs from type in outline and centre.

Pavonia, N. J., artesian well. Rare.

Pl. 25, Fig. 8.

{92}NAVICULA DELAWARENSIS GRUN.

Valve elliptical-lanceolate, with sub-rostrate ends; axial area narrow, lanceolate, widened in the middle; striæ about 10 in 10 µ; in the middle, much closer at the ends; puncta in the middle, 9 in 10 µ, closer and much smaller at the ends. L. 58-95 µ.

Cleve (Le Diatomiste, Vol. 2, p. 14) states that this form is very near N. pusilla but is much larger. Specimens from Smith's Island measure 58-65 µ, from Wildwood, 95 µ in length.

Pl. 25, Fig. 3.

NAVICULA PUNCTULATA WM. SM.

Valve elliptical-lanceolate, with sub-rostrate ends; axial area narrow, central area rounded; striæ, 11 in 10 µ, closer at the ends, a few shorter in the middle; puncta, 10 in 10 µ. L. 54 µ.

Navicula marina Ralfs.

Port Penn, Delaware River (brackish water).

Pl. 25, Fig. 9.

"Although this species is described as marine in the Synopsis of Prof. Smith, I have never found it in purely marine localities" (Donkin).

NAVICULA PUNCTATA VAR. ASYMMETRICA LAGERSTEDT

Valve lanceolate, with rostrate ends; axial area narrow, central area transverse, irregular; striæ radiate, punctate, 12 in 10 µ. L. 36 µ.

Navicula amphibola Cleve.

Blue clay.

Pl. 27, Fig. 15.

NAVICULA BRASILIENSIS VAR. BICUNEATA CL., FORMA CONSTRICTA

Valve oblong-elliptical, slightly constricted, with cuneate-rostrate ends; axial area narrow; central area dilated transversely and unilaterally; striæ, 9 in 10 µ; puncta closer at the border and in irregular longitudinal rows in the middle; terminal fissures small, hook-shaped, turned in the same direction. L. 93 µ.

Corresponds closely to Cleve's variety except in the constriction.

Blue clay.

Pl. 25, Fig. 2.

NAVICULA LACUSTRIS GREG.

Valve lanceolate, sub-acute; axial area narrow; central area orbicular; striæ radiate, 14 in 10 µ, punctate, the median puncta sometimes more distant than the others.

Blue clay. Rare.

Pl. 27, Fig. 12.

LYRATÆ CL.

Valve elliptical or elliptical-lanceolate; striæ punctate, transverse; axial area narrow or indistinct; central area expanded on each side into lyre-shaped or horn-like blank spaces.

NAVICULA PRÆTEXTA EHR.

Valve elliptical; lateral areas not regular, with scattered puncta; striæ radiate, 5 or 6 in 10 µ; puncta, 7 or 8 in 10 µ; along the axial area, a single or double row of puncta; at {93}the middle of the border, on each side, two striæ approach each other closely with a short stria between them; terminal fissures small, in the same direction. L. 120 µ.

Port Penn, Delaware River.

Pl. 24, Fig. 2.

While variable in size and striation, approaching N. hennedyi, this species, as here figured, is found in the Miocene and later deposits and is extant in most parts of the world.

NAVICULA IRRORATA GREV.

Valve oblong-elliptical, with cuneate-rostrate ends; striæ, 7 or 8 in 10 µ, puncta, 7 in 10 µ; axial area bordered by puncta in unequal, transverse rows. L. 84 µ.

Blue clay. Rare.

Pl. 24, Fig. 4.

NAVICULA HENNEDYI WM. SM.

Valve elliptical; areas semilanceolate; striæ about 11 in 10 µ, sometimes longer and shorter on the margin; short rows of transverse striæ along the axial area.

Blue clay.

Pl. 25, Fig. 12.

Var. circumsecta Grun.--As in the type but with the lateral areas faintly striate or punctate.

Var. manca A. S.--Valve lanceolate-elliptical, the lateral areas narrow and convergent toward the ends; short rows of transverse striæ along the axial area; striæ, 9 in 10 µ; central pores incrassate.

Blue clay.

Pl. 25, Fig. 11.

NAVICULA LYRA EHR.

Valve elliptical, with rounded, sub-rostrate or sub-cuneate ends; lateral areas narrow; striæ, 6 to 14 in 10 µ (Cl.), punctate. L. 50-180 µ.

Var. ehrenbergii Cl.--Lateral areas constricted in the middle, divergent at the ends. Cleve refers to Schmidt, Atlas, Pl. 2, Fig. 25, which is not divergent at the ends.

Along the coast.

Pl. 25, Fig. 10.

A narrower form occurs which has the areas divergent.

Var. ?--Valve elliptical, lateral areas narrow, convergent at the ends with short rows of punctate striæ; marginal striæ, 10 in 10 µ, punctate. L. 60 µ.

Squan River, N. J.

Pl. 20, Fig. 5.

Var. dilatata A. S.--Valve elliptical, rostrate; lateral areas convergent in the middle and nearly parallel or convergent at the ends.

Blue clay.

Pl. 25, Fig. 13.

N. lyra is exceedingly variable in outline, fineness of striation and in the lateral areas. Intermediate forms occur approaching N. hennedyi and N. spectabilis. In N. hennedyi the lateral areas are broad, semilanceolate, not narrowed in the middle. In N. spectabilis the lateral areas are broad and narrowed in the middle. In N. lyra the lateral areas are narrow and either constricted or not in the middle. In many forms in {94}these three species the lateral areas are more or less striated or punctate. Cleve does not consider this a distinction of any importance, although certain varieties are founded upon it. All three species are very common in the blue clay and along the coast, but their varieties are too numerous to describe or figure.

NAVICULA SPECTABILIS VAR. EMARGINATA CL.

Valve elliptical; lateral areas broad, narrowed in the middle, delicately striated; marginal striæ, 10 in 10 µ. L. 70 µ.

Blue clay.

Pl. 25, Fig. 7.

NAVICULA PYGMÆA KUETZ.

Valve elliptical, appearing hyaline; axial and central areas faint; lateral areas convergent in the middle; striæ indistinct, about 25 in 10 µ. L. 23 µ.

Brandywine Creek (Palmer).

Pl. 27, Fig. 23.

DECUSSATÆ CL.

Valve elliptical or lanceolate; axial area narrow; central area small; striæ punctate, in transverse and oblique, curved rows.

NAVICULA PLACENTA EHR.

Valve elliptical, with short, rostrate-capitate ends; axial area narrow; central area elliptical; striæ in two directions, the transverse about 22 (to 27, Cl.) in 10 µ, the oblique striæ crossing in both directions in curved lines appearing "coarser than the transverse" (Lewis).

A very peculiar species which, as Cleve remarks, seems not to be allied to any other. L. about 35 µ, quite constant in size. It is reported from Finland, Scotland, Hungary and New Zealand. Dr. Lewis found it in the Delaware River. It is occasional in the Schuylkill River and the blue clay, and very abundant on Marchantia and mosses on the wet rocks of the upper Wissahickon (F. J. Keeley).

Pl. 27, Fig. 17.

LINEOLATÆ CL.

Valve more or less lanceolate; axial area narrow or indistinct; striæ radiate or parallel, lineate, that is, with the puncta closer than the striæ.

NAVICULA RADIOSA KUETZ.

Valve lanceolate with sub-rostrate apices; axial area indistinct; central area small; striæ radiate in the middle, from 6 to 8 in 10 µ, and convergent at the ends, about 12 in 10 µ. L. 47 µ.

Very common in fresh water.

Pl. 26, Fig. 17; Pl. 40, Fig. 9.

NAVICULA PEREGRINA EHR.

Valve lanceolate, obtuse; axial area narrow; central area large, rounded or slightly irregular; striæ coarse in the middle, 5 in 10 µ, radiate; convergent at the ends, 7 or 8 in 10 µ.

Abundant in brackish water. Delaware River.

Pl. 26, Fig. 20.

{95}NAVICULA CYPRINUS (WM. SM.)

Valve lanceolate, slightly gibbous in the middle, sub-cuneate at the ends; axial area narrow; central area small; striæ radiate in the middle, 10 in 10 µ, with shorter, transverse striæ intermediate; transverse at the extreme ends. L. 82 µ.

Navicula digito-radiata var. cyprinus (Ehr. ?) Wm. Sm. Whether the form here figured is Ehrenberg's or not, it is the species known as Pinnularia cyprinus Ehr. of Wm. Smith.

Common in Shark River, N. J.

Pl. 26, Fig. 21.

NAVICULA REINHARDTII GRUN.

Valve elliptical or elliptical-lanceolate, with broad, rounded ends; axial area narrow, widened at the ends to the width of the valve; central area widened transversely to an irregular, quadrate space; striæ coarse, 8 in 10 µ, distinctly lineate, alternately longer and shorter in the middle, radiate, nearly transverse at the ends. L. 59 µ.

Blue clay. Rare.

Pl. 26, Fig. 22.

NAVICULA LANCEOLATA VAR. ARENARIA (DONK.) CL.

Valve lanceolate; axial area very narrow or indistinct; central area small, rounded; striæ radiate, 11 in 10 µ in the middle, closer at the ends. L. 47-54 µ.

Navicula arenaria Donk.

Shark River, N. J.

Pl. 26, Fig. 23.

NAVICULA SALINARUM GRUN.

Valve elliptical-lanceolate with produced sub-capitate or rostrate ends; striæ radiate in the middle, longer and shorter; transverse at the ends, lineate. L. 32 µ.

Atlantic City, N. J.

Pl. 26, Fig. 24.

NAVICULA VIRIDULA VAR. ROSTELLATA KUETZ.

Valve lanceolate with rostrate ends; axial area very narrow, central area orbicular; striæ radiate in the middle, about 12 in 10 µ, convergent at the ends and closer. L. 43 µ.

Common in fresh water.

Pl. 26, Fig. 16.

NAVICULA GRACILIS VAR. SCHIZONEMOIDES (EHR.) V. H.

Valve lanceolate, obtuse; axial area widened in the middle; striæ radiate in the middle, about 12 in 10 µ, transverse or slightly convergent at the ends. L. 45-60 µ. Occurs in gelatinous tubes; usually found free.

Colletonema neglectum Thwaites.

Fresh water.

Pl. 26, Fig. 19.

NAVICULA RAMOSISSIMA (AG.) CL.

Valve lanceolate, sub-acute; axial area very narrow; central area scarcely widened; striæ, 12 in 10 µ, parallel throughout. L. 45 µ.

Micromega ramosissimum Ag.

Schizonema smithii Kuetz. (not Ag.).

East River, N. Y.

Pl. 26, Fig. 14.

{96}NAVICULA ANGLICA RALFS

Valve elliptical, with sub-capitate or rostrate ends; axial area narrow, central area small; striæ radiate, 12-13 in 10 µ, distinctly punctate. L. 26 µ.

Fresh water.

Pl. 26, Fig. 26.

NAVICULA GASTRUM EHR.

Valve elliptical, with rostrate ends; axial area narrow, central area transverse or irregular; striæ radiate, 9 in 10 µ in the middle. L. 26 µ.

The form here figured approaches N. anglica.

Kirkwood Pond, N. J.

Pl. 26, Fig. 25.

NAVICULA DICEPHALA WM. SM.

Valve linear, with rostrate or rostrate-capitate ends; axial area narrow, central area rectangular, transverse; striæ radiate, 12 in 10 µ. L. 32 µ.

Fresh water.

Pl. 27, Fig. 16.

NAVICULA HUMILIS DONK.

Valve elliptical, with broad, rostrate ends; axial area narrow; central area small; striæ radiate and distant in the middle, convergent at the ends, coarse, appearing costate, averaging 9 in 10 µ. L. 19 µ. As Donkin states, the striæ are "very conspicuous."

Navicula hungarica var. capitata (Ehr.) Cl.

Navicula globiceps Lagerstedt, according to Cleve.

Willistown, Pa.

Pl. 27, Fig. 24.

NAVICULA PINNATA PANT. ?

Valve lanceolate, obtuse; axial area narrow, widened in the middle; striæ coarse, 7 in 10 µ in the middle, radiate, 10 in 10 µ at the ends and transverse, indistinctly lineate. L. 40 µ.

Near Navicula ardua Mann (Diat. Albatross Voy., Cont. U. S. Nat. Herbarium Vol. 10, Part 5, p. 336, Pl. 53, Fig. 2) which, however, is said to have "strictly unbeaded costæ."

Pavonia, N. J., artesian well.

Pl. 27, Fig. 20.

NAVICULA PENNATA A. S.

Valve lanceolate, acute; axial area narrow; central area quadrate, transverse; striæ radiate, coarse, 5 in 10 µ, lineate. L. 68-95 µ (Cleve).

Pavonia, N. J., artesian well.

Pl. 27, Fig. 22.

NAVICULA INFLEXA GREG.

Valve slightly elliptical-lanceolate, sub-acute, smooth at the ends; axial area narrow, widened in the middle; striæ radiate, 11 in 10 µ, lineate. Frustule in zone view constricted in the middle. L. 28-45 µ.

Common along the coast.

Pl. 27, Figs. 18 and 19.

{97}NAVICULA OBLONGA KUETZ.

Valve linear-lanceolate, with broad, rounded ends; margin sometimes undulate; axial area narrow; central area large, orbicular; striæ in the middle distant, radiate, convergent at the ends and curved or sharply bent, 7 in 10 µ, lineate. L. 70-200 µ (Cleve).

Blue clay. Occasional in fresh water.

Pl. 27, Fig. 21.

NAVICULA HASTA PANT.

Valve lanceolate, gently tapering to the obtuse, produced ends; axial area lanceolate, widened to an orbicular space in the middle; striæ radiate, the median coarse and quite distant, 5 in 10 µ, becoming closer at the ends where they are 12 in 10 µ, lineate. The distance between the median striæ gives the appearance of a stauros.

Occasional in the blue clay.

Pl. 27, Fig. 13.

NAVICULA HASTA VAR. PUNCTATA N. VAR.

Valve as in type but with striæ in the middle distinctly punctate and reaching the median line.

Greenwich Point, Philadelphia.

Pl. 27, Fig. 14.

NAVICULA RHYNCOCEPHALA KUETZ.

Valve lanceolate, with produced ends; axial area indistinct; central area small, rounded; striæ radiate in the middle, convergent at the ends, 10-11 in 10 µ, punctate. L. 42 µ.

Fresh water. Common.

Pl. 31, Fig. 8.

NAVICULA CRYPTOCEPHALA KUETZ.

Valve lanceolate, with rostrate ends; axial area indistinct; central area small; striæ, 16 in 10 µ, lineate, radiate in the middle, convergent at the ends. L. 28 µ.

Common in fresh water.

Intermediate forms occur between N. rhyncocephala and N. cryptocephala.

Pl. 31, Fig. 9.

NAVICULA LONGA (GREG.) RALFS

Valve slender, rhombic, elongated, with acute ends; axial area indistinct; central area small; striæ, 6 or 7 in 10 µ, radiate in the middle, elsewhere transverse; central pores closely approximate. L. 120 µ.

New Rochelle, N. Y.

Pl. 31, Fig. 10.

Cleve refers this form to N. directa var. remota Grun. Some specimens are found in this locality showing the "generally twisted" median line mentioned by Gregory.

MESOLEIÆ CL.

Valve linear or elliptical; axial area narrow; central area quadrate; striæ radiate, finely punctate.

NAVICULA MUTICA KUETZ.

Valve ovate, elliptical or lanceolate; axial area narrow; central area dilated into a stauros not reaching the margin; striæ about 20 in 10 µ, more distant in the middle, radiate, punctate. A punctum occurs on one side of the central nodule.

{98}Reported from New Jersey in fresh water. I have not found it. The figure is from a specimen from another locality.

Pl. 26, Fig. 6.

NAVICULA MINIMA GRUN.

Valve broadly elliptical, 13-15 µ in length; axial area narrow; central area small but with a quadrate pseudo-stauros which is striated; striæ, about 28 in 10 µ, radiate.

Agrees closely with N. saugeri var. Grun. in V. H. Synopsis, Pl. 14, Fig. 16, said to be intermediate between N. minima and N. atomoides Grun. N. minima var. atomoides Grun. is smaller.

Common in water-troughs.

Pl. 26, Fig. 13.

NAVICULA PUPULA VAR. BACILLARIOIDES GRUN.

Valve linear, with rounded ends; axial area linear, expanding on both sides near the ends of the valve, forming a transverse lunate space; central area small, apparently expanded into a stauros, which, however, is striated; striæ, 18 in 10 µ, at the middle, closer at the ends, punctate. L. 54 µ.

Pavonia, N. J., artesian well.

Pl. 26, Fig. 9.

BACILLARES CL.

Valve linear or linear-elliptical, with broad ends; axial area narrow, the median line enclosed in siliceous ribs; striæ finely punctate, more distant in the middle.

NAVICULA BACILLUM EHR.

Valve linear, with rounded ends; axial area enclosed in siliceous ribs and slightly expanded on each side at the ends; terminal nodules incrassate; central area small, elliptical; striæ, 15 in 10 µ in the middle, transverse, distinctly punctate, closer at the ends L. 47 µ.

Fresh water.

Pl. 26, Fig. 10.

Cleve describes the form as having slightly radiate striæ in the middle. There is considerable difference in the descriptions of Cleve, Donkin, Grunow and Van Heurck, as also in all of the figures.

NAVICULA AMERICANA EHR.

Valve oblong-linear, with rounded ends, sometimes slightly constricted; axial area about one-half the width of the valve, dilated in the middle; striæ parallel in the middle, radiate at the ends, 15-16 in 10 µ. A punctum is usually found in the central nodule. L. 55-154 µ.

Blue clay. Occasional in fresh water.

Pl. 26, Fig. 8.

DECIPIENTES CL.

Valve lanceolate, with obtuse ends; axial area narrow; central area orbicular; striæ radiate in the middle and more distant.

NAVICULA SEMEN EHR.

Valve elliptic-lanceolate, with sub-rostrate, truncate apices; axial area narrow, {99}sinuous; central area orbicular; terminal fissures small, hook-shaped; striæ robust, 7 or 8 in the middle, closer at the ends, indistinctly punctate or lineolate.

Blue clay. Not common.

Pl. 26, Fig. 11.

Cleve states that this form belongs to the post-glacial deposits and is found living only in the Hartz Mountains.

NAVICULA INTEGRA WM. SM.

Valve lanceolate with triundulate margins and rostrate-apiculate ends; striæ radiate, more distant in the middle, 20-23 in µ, punctate; axial area very narrow, central area rounded or elliptical. L. 33-43 µ.

Pavonia, N. J., artesian well. Common in Chester River, Md.

Pl. 26, Fig. 5.

MICROSTIGMATICÆ CL.

Valve lanceolate; axial area narrow; central area small, rounded; striæ finely punctate, nearly parallel. (Includes here only the division Libellus.)

NAVICULA TUMIDA (BRÉB.) CL.

Valve lanceolate, with rounded ends; axial area narrow, central area elliptical; raphe slightly sigmoid; striæ, 13 in 10 µ, finely punctate, a few shorter in the middle.

Scoliopleura tumida (Bréb.) V. H.

Cape May, N. J.

Pl. 25, Fig. 1.

NAVICULA GREVILLEI (AG.) CL.

Frustules in gelatinous tubes, rectangular; zone with numerous longitudinal divisions. Valve elliptical-lanceolate, obtuse; axial area narrow, central area small; striæ lineate, about 18 in 10 µ in the middle where they are slightly radiate and more evident, closer near the ends and transverse; median line with terminal pores distant from the ends. L. 60 µ.

Schizonema grevillei Ag.

East River, N. Y.

Pl. 31, Figs. 3 and 4.

NAVICULA LIBELLUS GREG.

Valve rhombic-elliptical, obtuse at the ends; axial area narrow, central rounded, small; striæ punctate, slightly radiate, about 19 in 10 µ; terminal fissures close to the ends, indistinct. L. 60 µ.

Cleve describes this form as having acute ends, while Gregory states that it is "more obtuse and broader than N. rhombica." Gregory's Figure 101 apparently shows the ends acute, but he says that the valve view is "rhombic or elliptic-lanceolate, broad, with obtuse ends" (Diat. of the Clyde, p. 57, Pl. 6).

Hackensack Swamp, N. J.

Pl. 31, Fig. 5.

ORTHOSTICHÆ CL.

Valve lanceolate or elongated; axial area narrow; central area sometimes apparently dilated into a stauros; striæ punctate, the puncta in transverse and longitudinal rows.

{100}NAVICULA CUSPIDATA KUETZ.

Valve rhombic-lanceolate, with acute ends; axial area linear, narrow, not widened in the middle; striæ transverse, 14-19 in 10 µ (Cl.). L. 70-150 µ.

Blue clay. Not uncommon in fresh water.

Pl. 26, Figs. 1 and 2.

Fig. 2 represents an inner valve or stratum, with strong costæ variable in size, formerly known as Surirella craticula Ehr.

N. cuspidata var. ambigua (Ehr.) Cl.--Valve elliptical-lanceolate, with rostrate ends, smaller than the type and with finer striæ.

Crum Creek.

Pl. 26, Fig. 3.

NAVICULA SPICULA (HICKIE) CL.

Valve narrow, lanceolate with acute ends; axial area narrow, central area dilated into a stauros reaching the margin; transverse striæ, 25-29 in 10 µ, longitudinal closer. L. 50-130 (Cl.).

Sometimes confused with N. crucigera.

Stauroneis spicula Hickie.

Newark, N. J.

Pl. 26, Fig. 4.

NAVICULA CRUCIGERA (WM. SM.) CL.

Valve lanceolate, narrow, with acute apices; central nodule a stauros reaching the margin but crossed by two or three coarser striæ; transverse striæ, 12 in 10 µ, punctate, the puncta about 25 in 10 µ. L. 80-100 µ (Cl.). Frustules in gelatinous tubes or free.

Schizonema cruciger Wm. Sm.

Pl. 26, Fig. 15.

Reported as occurring in New York Bay, but I have not seen it. The figure is from a specimen from another locality.

MINUSCULÆ CL.

Valve lanceolate or elliptical, chiefly distinguished by the small size; axial area indistinct; central area small; striæ radiate, very finely punctate.

NAVICULA ATOMUS NÆGELI

Valve elliptical, 6-8 µ in length; striæ radiate, 26-30 µ, closer near the ends; axial area linear, scarcely widened in the middle.

Water-troughs and ditches. Probably common, but frequently not noticed because of its minuteness. A mounting medium of the highest refractive index, such as realgar, is required to resolve the striæ. In the figure the striæ are drawn a little coarser than they appear in most specimens.

Pl. 26, Fig. 12.

LÆVISTRIATÆ CL.

Valve lanceolate, axial area distinct; central area orbicular; striæ coarse, indistinctly punctate, approaching the costæ of Pinnularia.

{101}NAVICULA YARRENSIS GRUN.

Valve elliptical-lanceolate, with rounded ends; axial area lanceolate, widened in the middle; striæ, 5 in 10 µ. L. 97 µ.

Cape May, N. J. Common.

Pl. 25, Fig. 14.

Fig. 15, a smaller form, 65 µ in length; striæ, 6 in 10 µ.

Fig. 16, 54 µ in length; striæ, 8 in 10 µ (near var. valida Pant.).

NAVICULA ELEGANS WM. SM.

Valve elliptical-lanceolate, with produced ends; axial area very narrow, central area large, orbicular; striæ strongly divergent in the middle, slightly, if at all, convergent at the ends, curved toward the margin, indistinctly lineate, 9 in 10 µ. L. 95 µ.

Blue clay. Not rare.

Pl. 31, Fig. 1.

Navicula elegans var. cuspidata Cl.--Valve as in type form but smaller and with rostrate apices; striæ, 10 in 10 µ. L. 82 µ.

Belmar, N. J.

Pl. 31, Fig. 2.

Cleve remarks that the type form is acute and the striæ 9, while the var. cuspidata has 12 striæ in 10 µ. In Fig. 1, Pl. 31, is represented a valve having 9 striæ in 10 µ, but not acute, while Fig. 2, with but slight variation in striæ, is more cuspidate. It is probable there are intermediate variations.

NAVICULA PALPEBRALIS BRÉB.

Valve elliptical-lanceolate, with acute apiculate ends; axial area broad, lanceolate; striæ radiate, lineate, about 11 in 10 µ. L. 60 µ.

Along the coast.

Pl. 31, Figs. 6 and 7.

On Plate 40, Fig. 5, is represented an abnormal form of Navicula in which the central pores are in a line transverse to the longitudinal axis and each raphe is curved in a line which almost returns to the centre. The puncta are in curved lines radiating from the rounded hyaline centre.

Pavonia, N. J., artesian well.

Weissflog has described valves of Navicula somewhat similar in punctation.

PINNULARIA EHR. (1843)

(pinnula, a small feather)

Valve linear or nearly so, with rounded ends; axial area broad; central and terminal areas large; costæ smooth, transverse or radiating, usually convergent at the ends.

The costæ are channels on the inside of the valve, closed, except in the middle where elliptical foramina, opening into the interior of the valve, give rise through their terminal margins to the two longitudinal lines on each side of the valve. The raphe begins as a groove in the side of the conical central nodule and continues as a cleft at right angles to the plane of the surface of the valve, in which case the raphe forms a single line; if the raphe is inclined to the valve surface, then two lines appear in projection, the upper and lower edges of the cleft. In some forms the surface of the edge of the raphe on one side is folded or grooved for a considerable distance, and the opposite edge is elevated into a ridge or {102}tongue fitting into the groove. In such cases it is possible, in projection, to see the upper or outer edges of the raphe, the lower edges and the edges of the tongue and groove, thus showing four lines; sometimes, when the tongue and groove do not meet, six lines. The so-called inner channel is the part of the raphe on the inside of the tongue, and the so-called exterior channel is the part of the raphe on the outside of the tongue. If, in addition to this formation of the raphe, the plane of cleavage changes toward the terminal nodules, the lines will cross each other and, when two are superimposed, disappear altogether. For the careful examination of the raphe it is necessary to employ large forms, and it is advisable to use nitrate of silver which remains in the raphe, and, as in slides mounted by Mr. F. J. Keeley, shows in a beautiful manner the entire outline of raphe and fissures. The terminal fissures owe their separation to the different directions taken by the two edges of the raphe on each side, one edge bending in a wide curve toward the end of the valve, showing two lines, the upper and lower edges of one side of the raphe when inclined to the plane of the surface, and the other edge of the raphe turning suddenly in an opposite direction and ending abruptly in a curve, giving rise to the appearance, by diffraction, of a punctum.

Pl. 40, Figs. 13, 14 and 15.

Endochrome consists of two chromatophores lying on the zones.

Pinnularia is usually divided into the Majores, or larger, and the Minores, or smaller forms, the latter being further divided according to their striæ. The following classification is chiefly that of Cleve.

Majores.--Valve large, linear with parallel or slightly radiate striæ and broad axial area.

Gracillimæ.--Valve small, striæ parallel or nearly so; axial area very narrow.

Capitatæ.--Valve with capitate or rostrate ends; striæ radiate.

Divergentes.--Striæ strongly radiate.

Brevistriatæ.--Striæ short.

Distantes.--Striæ distant.

Tabellariæ.--Striæ radiate in the middle, strongly convergent at the ends.

Marinæ.--Marine forms.

MAJORES

PINNULARIA MAJOR (KUETZ.) WM. SM.

Valve linear, usually slightly gibbous in the middle and at the ends; raphe oblique; axial area less than one-third the width of valve, convergent at the ends; striæ, 7 or 8 in 10 µ, radiate in the middle, convergent at the ends, crossed by a narrow band. L. ? to 300 µ.

Blue clay. Fresh water. Abundant at Middletown, Delaware Co. (T. C. Palmer).

Pl. 28, Fig. 4.

Fig. 9, Pl. 29, is one of a number of smaller forms which are difficult to determine, approaching P. viridis.

PINNULARIA MAJOR VAR. PULCHELLA N. VAR.

Valve strongly gibbous in the middle and gradually widened to the rounded ends; axial area broad, less than one-third the width of the valve, widened unilaterally in the middle; striæ, 7 in 10 µ, crossed by a band nearly as wide as the length of the costæ and scarcely distinct. L. 273 µ.

{103}The central nodule is scarcely evident, probably because it is not so thick as in other forms. The outline is near to that of N. mesogongyla and certain forms of N. nobilis, differing from the latter in the median line, striæ and band which is wider than that of P. latevittata var. domingensis Cl.

Hammonton Pond, N. J.

Pl. 28, Fig. 2.

A very beautiful form which I cannot find described or figured. It does not appear to be N. major var. turgidula Cl., which has a narrow band. In the fossil deposit from Hopkinton, N. H., valves occur similar in outline but smaller.

PINNULARIA NOBILIS EHR.

Valve slightly gibbous in the middle and at the ends; median line complex; striæ, 4 or 5 in 10 µ, slightly convergent or parallel at the ends, crossed by a band one-third as wide as the length of the striæ. L. ? to 350 µ.

Blue clay. Fresh water.

Pl. 28, Fig. 1.

PINNULARIA DACTYLUS EHR.

Valve broad, linear, slightly gibbous in the middle; ends broad, rounded; median line not complex, sinuous; striæ, 4 or 5 in 10 µ, crossed by a very broad band. L. ? to 300 µ.

Navicula gigas A. S.

Blue clay. Fresh water.

Pl. 28, Fig. 3.

Forms occur which are with difficulty assigned to either nobilis or dactylus.

PINNULARIA DACTYLUS VAR. DARIANA (A. S.) CL.

Valve linear-lanceolate, obtuse; axial area broad, less than one-third the width of the valve; striæ, 6 in 10 µ, crossed by a broad band. L. 220 µ.

Absecon, N. J.

Pl. 29, Fig. 3.

PINNULARIA DACTYLUS VAR. DEMERARÆ CL.

Valve elliptical-lanceolate, with sub-cuneate ends; axial area lanceolate, broad in the middle; median line flexuose; striæ radiate throughout, 6 in 10 µ. L. 150 µ.

Blue clay.

Pl. 29, Fig. 10.

PINNULARIA GENTILIS (DONK.) CL.

Valve linear, with rounded ends; axial area about one-fourth the diameter of the valve; striæ radiate in the middle, convergent at the ends, 7 in 10 µ, crossed by a broad indistinct band.

Fresh water. Not common.

Pl. 29, Fig. 1.

PINNULARIA TRIGONOCEPHALA CL.

Valve linear, gibbous in the middle and at the cuneate ends; axial area wider between the middle and the ends, dilated to an elliptical space in the middle; striæ, 6 in 10 µ. L. 145 µ.

Blue clay.

Pl. 29, Fig. 8.

{104}PINNULARIA VIRIDIS NITZSCH

Valve linear-elliptical, with rounded ends; axial area narrow, widened in the middle; striæ, 6 to 7 in 10 µ, crossed by a band as wide as one-third the length of the striæ.

Common in fresh water.

Pl. 29, Fig. 2.

Quite variable in size. Approaches P. major by intermediate forms as in Fig. 9, Pl. 29.

PINNULARIA VIRIDIS VAR. FALLAX CL.

Valve linear, with rounded ends; axial area narrow, slightly widened in the middle; striæ sometimes unilaterally interrupted, nearly parallel, 10 in 10 µ.

Elm, N. J.

Pl. 29, Fig. 4.

In Fig. 2, Pl. 30, a form is represented which corresponds closely to Navicula viridis var. B, of Wm. Smith. It is given as synonymous with var. fallax; it is bilaterally interrupted. Blue clay.

PINNULARIA VIRIDIS VAR. ?

Valve linear-elliptical, with rounded ends; axial area narrow, widened in the middle to a transverse fascia which is sometimes unilateral; striæ, 14, in the middle, divergent, convergent at the ends and closer, crossed by a narrow band. L. 45-60 µ. Fascia sometimes absent or very narrow.

Northbrook, Pa.

Pl. 30, Fig. 17 (represents a form with wider area than usual).

PINNULARIA VIRIDIS VAR. CAUDATA N. VAR.

Valve elliptical-lanceolate, with sub-rostrate ends; axial area narrow, widened to an orbicular space in the middle; striæ radiate in the middle, 11-12 in 10 µ, convergent and closer at the ends, crossed by a narrow band; median line with very long terminal fissures; terminal nodules noticeable because of the thickening of the edges of the terminal striæ. L. 43 µ.

Fresh water, Newtown Square. Not common.

Pl. 30, Fig. 18.

PINNULARIA SOCIALIS (PALMER)

Valve linear, with rounded ends; axial area broad, one-third the width of the valve; striæ slightly radiate in the middle, convergent at the ends, elsewhere parallel, 8 in 10 µ, crossed by an indistinct band about one-third the length of the striæ. L. 60-120 µ.

This species, discovered by Mr. Palmer near Media, Pa., is remarkable for the grouping of the frustules "held with girdle sides together by a siliceous cementing of valve edges and enclosed in a common coleoderm." The usual number included in a group is four, but sometimes six or eight are noticed. The frustules adhere near their ends and are so firmly fastened that boiling in nitric acid and bichromate of potash for fifteen minutes will not separate them.

Navicula socialis Palmer (Proc. Acad. Nat. Sci., Phila., 1910, p. 460, Pl. 35).

Media, Pa.

Pl. 29, Fig. 5.

{105}PINNULARIA ÆSTUARII CL.

Valve linear, with rounded ends; axial area broad, less than one-third the width of the valve; central area a transverse fascia; striæ, 7 in 10 µ, parallel except at the ends where they are slightly convergent; median line flexuose, with short, terminal semicircular fissures. L. 85 µ.

Port Penn, Delaware River. Rare.

Pl. 29, Fig. 6.

GRACILLIMÆ

PINNULARIA MOLARIS (GRUN.) CL.

Valve very convex, linear, with sub-cuneate ends; axial area narrow, expanded in the middle to a transverse fascia reaching the margin; striæ divergent in the middle, convergent at the ends, 16 in 10 µ. L. 60 µ.

Fresh water.

Pl. 29, Fig. 15.

PINNULARIA LEPTOSOMA GRUN.

Valve linear, rounded at the ends; axial area narrow; central area a broad transverse fascia; striæ slightly divergent in the middle and convergent at the ends, 17 in 10 µ in the middle, closer at the ends. L. 56 µ.

Fresh water. Not common.

Pl. 30, Fig. 10.

CAPITATÆ

PINNULARIA MESOLEPTA EHR.

Valve linear, with triundulate margins and capitate ends; axial area narrow, widened in the middle; striæ divergent in the middle, convergent at the ends, about 12 in 10 µ. L. 34 µ.

Common in fresh water.

Pl. 29, Fig. 13.

PINNULARIA MESOLEPTA VAR. STAURONEIFORMIS GRUN.

Valve triundulate, capitate; axial area narrow, widened in the middle to a transverse fascia, broader at the margin; striæ strongly divergent in the middle and convergent at the ends, 9-10 in 10 µ. L. 70 µ.

Pavonia, N. J., artesian well. Fresh water.

Pl. 30, Fig. 20.

PINNULARIA SUBCAPITATA GREG.

Valve linear or linear-elliptical, with sub-capitate ends; axial area distinct, widened to a transverse fascia in the middle; striæ divergent in the middle, convergent at the ends, 13 in 10 µ. L. 32 µ.

Fresh water.

Pl. 29, Fig. 20.

{106}PINNULARIA SUBCAPITATA VAR. PAUCISTRIATA GRUN.

Valve linear-elliptical, with rounded ends; axial area gradually widened into a broad, transverse fascia; striæ divergent in the middle, convergent at the ends, 11-12 in 10 µ. L. 47 µ.

Fresh water.

Pl. 30, Fig. 16.

PINNULARIA TERMES (EHR.) A. S.

Valve linear, with concave margins and rostrate-capitate ends; axial area narrow, widened in the middle to an orbicular or sub-quadrate space; striæ divergent in the middle, scarcely, if at all, convergent at the ends, 10 in 10 µ.

Pensauken, N. J., artesian well.

Pl. 29, Fig. 17.

This is, I believe, the form figured by Schmidt (Atlas, Pl. 45, Fig. 67). Cleve refers it to Pinnularia interrupta forma biceps, in which the central space is rhomboid.

PINNULARIA TERMES VAR. STAURONEIFORMIS V. H.

Valve linear, with concave margins and capitate-rostrate ends; axial area narrow, widened into a rhomboidal fascia, reaching the margin; striæ, 10 in 10 µ, divergent in the middle, convergent at the ends.

Pinnularia interrupta forma stauroneiformis Cl.

Fresh water.

Pl. 29, Fig. 14.

PINNULARIA APPENDICULATA (AG.) CL.

Valve linear, with subcapitate ends; axial area narrow; central area a transverse fascia; striæ divergent in the middle, convergent at the ends, 16 in 10 µ. L. 43 µ.

Fresh water. Marl pits, Lenola, N. J. (Palmer).

Pl. 29, Fig. 18.

PINNULARIA BRAUNII GRUN.

Valve linear-lanceolate, with capitate ends; axial area gradually widened toward the middle and expanded into a fascia reaching the margin; striæ divergent in the middle, convergent at the ends, 11 in 10 µ. L. 52 µ.

Pensauken, N. J., artesian well.

Pl. 29, Fig. 16.

PINNULARIA MICROSTAURON (EHR.) CL.

Valve convex, linear, tapering to sub-cuneate or sub-rostrate ends; axial area very narrow; central area a broad fascia; striæ divergent in the middle, convergent at the ends, 12 in 10 µ. L. 35 µ.

Pavonia, N. J., artesian well.

Pl. 29, Fig. 19.

This form does not exactly correspond to Cleve's diagnosis, as the ends are not broad. All species in the group Capitatæ are quite variable.

{107}DIVERGENTES

PINNULARIA DIVERGENS VAR. ELLIPTICA GRUN.

Valve linear, with rounded ends; axial area widened in the middle to a transverse fascia; striæ, 9 in 10 µ, divergent in the middle, convergent at the ends. L. 150 µ.

Fresh water. Not common in this locality.

Pl. 31, Fig. 13.

PINNULARIA CARDINALICULUS CL.

Valve linear, with rounded ends; axial area wide, less than one-third the width of the valve, expanded to a transverse fascia; striæ divergent in the middle and slightly convergent at the ends, 9 in 10 µ. L. 97 µ.

Blue clay.

Pl. 30, Fig. 1.

As a rule, the median fissures in Pinnularia are turned inwards on the side of the longer edge of the terminal fissures, but not always. In this specimen the median fissures are turned slightly toward the side of the shorter edge of the terminal fissures.

PINNULARIA LEGUMEN EHR.

Valve linear, with more or less triundulate margins and broad, capitate ends; axial area less than one-fourth the width of valve, widened in the middle; striæ strongly divergent in the middle and convergent at the ends, 10 in 10 µ. L. 84 µ.

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

Pl. 30, Fig. 3.

PINNULARIA LEGUMEN VAR. ?

Valve as in type, but with a transverse fascia; striæ, 10 in 10 µ, curved or bent near the ends. L. 84 µ.

This form is not var. florentina Grun.

May's Landing, N. J. (with the type).

Pl. 30, Fig. 4.

PINNULARIA BRÉBISSONII (KUETZ.) CL.

Valve linear-elliptical, with rounded ends; axial area narrow, widened into a transverse fascia which is usually broader at the ends; striæ divergent in the middle, convergent at the ends, about 12 in 10 µ. L. 40-60 µ (Cl.).

Fresh water. Common.

Pl. 29, Fig. 12; Pl. 31, Fig. 11.

Variable in outline.

PINNULARIA MORMONORUM (GRUN.)

Valve linear, with rounded ends; striæ divergent in the middle, convergent at the ends, 10 in 10 µ; axial area rhombic-lanceolate, widened to a fascia usually reaching the border. L. 62 µ.

Navicula mormonorum Grun.

Common near Willistown, Pa.

This form is regarded by Cleve as P. brébissonii, but the axial area appears to distinguish it. The valves are sometimes narrowed in the middle.

Pl. 29, Fig. 11.

{108}BREVISTRIATÆ

PINNULARIA ACROSPHÆRIA (BRÉB.) CL.

Valve linear, gibbous in the middle and at the ends; axial area about half the width of the valve; median line with approximate central pores; median area punctate; striæ nearly parallel, radiate at the ends, 9 in 10 µ. L. 32-180 µ (Cl.).

Blue clay. Recent, fresh water.

Pl. 30, Fig. 7.

PINNULARIA ACROSPHÆRIA VAR. TURGIDULA GRUN. ?

Valve strongly gibbous in the middle; ends rounded; striæ, 12-13 in 10 µ. L. 54 µ.

Blue clay, Gloucester, N. J., artesian well.

Pl. 30, Fig. 8.

PINNULARIA BLANDITA N. SP.

Valve linear, gibbous in the middle, and with rounded ends; striæ radiate in the middle, convergent at the ends, 13 in 10 µ; axial area about one-fourth the width of the valve, widened in the middle; median line with small semicircular terminal fissures. L. 65 µ.

Pavonia, N. J., artesian well. Rare.

Pl. 30, Fig. 25.

PINNULARIA PARVA (EHR.) CL. VAR. ?

Valve linear, tapering to the subcapitate ends; axial area broad, lanceolate; median line with approximate central pores and semicircular terminal fissures; striæ slightly divergent in the middle and convergent at the ends, 12 in 10 µ. L. 58 µ.

Differs from the type in having finer striæ.

Atco, N. J.

Pl. 30, Fig. 14.

PINNULARIA NODOSA FORMA CAPITATA CL.

Valve triundulate, with capitate ends; axial area about one-fourth the width of valve; striæ parallel, convergent at the ends, 10 in 10 µ, sometimes interrupted in the middle. L. 47 µ.

Fresh water. Common.

Pl. 30, Figs. 15 and 19.

PINNULARIA POLYONCA (BRÉB.) LEWIS

Valve with triundulate margins, more inflated in the middle, with capitate ends; axial area very broad; striæ marginal, short, 9 in 10 µ, divergent in the middle, convergent at the ends. L. 97 µ.

Kirkwood Pond, N. J.

Pl. 30, Fig. 21.

The description of Kuetzing (Species Algarum, p. 85), where he states that the margins are "triundulate, the median inflation larger, apices rounded-capitate," appears to sufficiently distinguish this species, which I believe to be the same as Brun's Navicula peripunctata, except that the form figured (Espèces Nouvelles, Pl. 16, Fig. 11) is interrupted in the middle, a common variation in these forms. Cleve makes Navicula polyonca Bréb. equal Pinnularia mesolepta, but at the same time he considers Lewis' form and also Brun's as equivalent to Navicula formica Ehr., and calls it Pinnularia nodosa var. formica Ehr. P. mesolepta has a narrower area than nodosa. I adhere to Lewis' identification, as in any case it is the form here figured and is nearly, if not quite, the same as Brun's species.

{109}DISTANTES

PINNULARIA LATA (BRÉB.) WM. SM.

Valve linear-elliptical, broad; axial area broad, widened in the middle; striæ slightly radiate in the middle, 3 in 10 µ; median line oblique, the terminal fissures hook-shaped. L. 86 µ.

Blue clay. Not uncommon.

Pl. 30, Fig. 23.

PINNULARIA BOREALIS EHR.

Valve linear, with rounded or sub-truncate ends; axial area about one-fourth the width of the valve, widened in the middle; median line with large hook-shaped terminal fissures; striæ, 4 or 5 in 10 µ. L. 54 µ.

Blue clay. Occasional in fresh water in a smaller form. Specimens occur intermediate between P. lata and P. borealis.

Pl. 30, Fig. 22; Pl. 31, Fig. 12.

PINNULARIA BOREALIS VAR. SCALARIS (EHR.) CL.

Valve narrow, linear; axial area broad, widened into a transverse fascia; striæ, 8 in 10 µ. L. 32 µ.

Fresh water.

Pl. 30, Fig. 24.

TABELLARIÆ

PINNULARIA STOMATOPHORA (GRUN.) CL.

Valve linear, with rounded ends; axial area less than one-third the width of the valve, gradually widened in the middle to a transverse fascia; on each side of the central nodule is a lunate space; striæ divergent in the middle, convergent at the ends, 13 in 10 µ; terminal fissures very long, bayonet shaped. L. 75 µ.

Cleve describes a variety continua as not interrupted. In some forms the fascia is marked by very faint, short striæ on the margin.

Fresh water. Newtown Square.

Pl. 30, Fig. 12.

PINNULARIA GIBBA (KUETZ.) V. H.

Valve linear, tapering to the subcapitate ends; axial area dilated in the middle; striæ, 10-11 µ, divergent in the middle, convergent at the ends. L. 80 µ.

Fresh water.

Pl. 30, Fig. 5.

PINNULARIA MESOGONGYLA (EHR.) CL.

Valve linear, gibbous in the middle, ends subcapitate; axial area narrow, widened in the middle to a large orbicular space; striæ strongly divergent in the middle, convergent at the ends, 11 in 10 µ. L. 60 µ.

Fresh water. Common.

Pl. 30, Fig. 6.

{110}PINNULARIA STAUROPTERA (GRUN.) CL.

Valve linear, with slightly triundulate margins tapering to the subcapitate ends; axial area more than one-third the width of the valve, slightly widened in the middle; median line with approximate central pores and semicircular terminal fissures; striæ divergent in the middle, convergent at the ends, 11 in 10 µ. L. 82 µ.

May's Landing, N. J.

Pl. 30, Fig. 13.

Some of the forms are more triundulate than the specimen figured.

PINNULARIA STAUROPTERA VAR. INTERRUPTA CL.

Valve linear, tapering to the subcapitate ends; axial area broad, widened in the middle to a transverse fascia; striæ divergent in the middle, convergent at the ends, 10 in 10 µ; median pores approximate. L. 118 µ.

Schuylkill River.

Pl. 30, Fig. 11.

PINNULARIA TABELLARIA (EHR.) CL.

Valve linear, gibbous in the middle and tapering to the subcapitate ends; axial area about one-third the width of the valve, widened in the middle; median line with approximate central pores and bayonet-shaped terminal fissures; striæ sometimes unilaterally interrupted, divergent in the middle, strongly convergent at the ends, 9 in 10 µ. L. 138 µ.

Blue clay. Rare.

Pl. 30, Fig. 9.

The form here figured has coarser striæ than in the type which is also usually more capitate.

P. legumen has triundulate margins, P. mesogongyla has an orbicular space, while P. gibba has the space widened. According to Cleve, P. gibba has approximate central pores, as has also P. mesogongyla. In what I have considered to be P. legumen, the central pores are more approximate than in the other two species mentioned. In fact, all of the three resemble each other closely, and are variously named by different authors. The form of P. gibba here figured, which may be P. stauroptera, is not the typical form of Wm. Smith, which has a narrow area and central space. There are, however, among the typical specimens in H. L. Smith's Type Slide No. 275, smaller valves which show a resemblance.

MARINÆ

PINNULARIA RECTANGULATA (GREG.) CL.

Valve linear, with abruptly rounded ends; axial area very narrow; central area large, somewhat quadrate; striæ, 7-8 in 10 µ. L. 78 µ.

Navicula rectangulata Greg.

Shark River, N. J.

Pl. 29, Fig. 7.

{111}EPITHEMIA BRÉB. (1838)

(epithema, a cover or lid)

Frustules epiphytic, solitary, sometimes geminate, adherent on the ventral side at the ends; in zone view rectangular, sometimes tumid in the middle. Valve arcuate, having an interior costate stratum or transverse septa extending to the girdle, often detached, and an exterior valve surface with transverse rows of puncta. Central and terminal nodules not easily seen; in some species a true raphe is indicated.

The resemblance between Epithemia and Eunotia has been already mentioned. In the shape and striation of the valves there is an approach to Cymbella.

The genus is divided into two groups, one in which the costæ alternate with double rows of puncta, as in E. turgida, and the other in which the rows of puncta are more than two.

The endochrome usually consists of a band lying along the ventral zone and extending in two flaps on the valves.

EPITHEMIA TURGIDA (EHR.) KUETZ.

Valve arcuate, with ends subcapitate; costæ radiate, 4 in 10 µ, alternating with double rows of puncta. Median nodule central, the raphe curved toward the ventral edge which it closely follows.

Parasitic on algæ. Very common in fresh water, especially in ponds. In the figure the valve is asymmetrical with respect to the transverse axis, an unusual condition.

Pl. 31, Fig. 14.

EPITHEMIA ARGUS KUETZ.

Valve with dorsal margin convex, and ventral margin nearly straight; ends rounded, constricted; costæ robust, alternating with more than two rows of puncta; zone view rectangular, the thickened ends of the costæ forming large nodules in a row along the edge of the valve next to the connecting zone.

Cystopleura argus (Ehr.) Kunze.

Common in fresh water.

Pl. 31, Figs. 15 and 21.

EPITHEMIA ARGUS VAR. ?

Valve strongly arcuate on the dorsal side and concave on the ventral; tapering to the rounded but not produced ends; costæ at unequal distances, about 2 in 10 µ; granules in transverse rows, 8 in 10 µ. L. 100 µ.

Pensauken, N. J., artesian well.

Pl. 31, Fig. 16.

EPITHEMIA MUELLERI A. S. ?

Valve broad, convex, slightly arcuate, with obtuse, somewhat constricted apices; costæ about 4 in 10 µ; striæ, 12-14 in 10 µ; in zone view the outline is rectangular, slightly tumid in the middle. L. 78 µ.

Blue clay.

Pl. 31, Fig. 17.

{112}EPITHEMIA ZEBRA VAR. PROBOSCIDEA (KUETZ.) GRUN.

Valve convex on the dorsal, concave on the ventral side; costæ, 3-4 in 10 µ, slightly radiating; apices recurved, capitate.

Blue clay.

Pl. 31, Fig. 18.

EPITHEMIA GIBBERULA VAR. PRODUCTA GRUN.

Valve narrow, lunate, with produced and arcuate apices; costæ radiate, 3-4 in 10 µ; striæ, 16-18 in 10 µ, punctate. L. 58 µ, usually smaller.

Blue clay.

Pl. 31, Fig. 19.

EPITHEMIA MUSCULUS KUETZ.

Valve short, strongly arcuate on the dorsal, concave on the ventral side; apices slightly produced; costæ radiate, about 5 in 10 µ; striæ, 15 in 10 µ, punctate. L. 20-60 µ.

Shark River, N. J.

Pl. 31, Fig. 20.

EPITHEMIA MUSCULUS VAR. CONSTRICTA (BRÉB.) V. H.

Frustule elliptical, slightly constricted in the middle. Valve convex on the dorsal, straight on the ventral side; costæ about 4 in 10 µ; striæ about 18 in 10 µ, finely punctate. L. 45 µ.

Epithemia succinta Bréb.

New Rochelle, N. Y.

Pl. 31, Fig. 22.

RHOPALODIA MUELLER (1885)

(Rhopalodes, like a war club)

Frustule in zone view linear, linear-elliptical (in our species), or clavate. Valve reniform or lunate; a raphe, not visible in some species in the usual position of the valve, is found along the convex edge or keel. Median and terminal nodules, although very small, can be determined. The name is more appropriate to the African species which are clavate. Two species only are found in this locality.

The chief distinction between Epithemia and Rhopalodia is in the position of the raphe and the nodules. In R. gibba and R. ventricosa the costæ are parallel and not radiate since the valves are not lunate.

Chromatophore a single band irregularly divided.

RHOPALODIA GIBBA (KUETZ.) MUELLER

Valve linear, arcuate on the dorsal, straight on the ventral side, reflexed at the extremities. Costæ, 6-7 in 10 µ; striæ about 14 in 10 µ. L. 80-200 µ.

Fresh water. Common.

Pl. 31, Fig. 23.

In this species the raphe and nodules can be seen only when the valve is examined at right angles to its usual position.

{113}RHOPALODIA VENTRICOSA (KUETZ.) MUELLER

Valve gibbous in the middle on the dorsal side, straight on the ventral side, with reflexed apices; costæ, 7 in 10 µ; striæ, 14-16 in 10 µ. L. 40-100 µ.

The median nodule appears as a minute depression in the middle of the dorsal side. The two species usually occur together.

Epithemia gibba var. ventricosa Kuetz.

Pl. 31, Fig. 24.

SURIRELLOIDEÆ

The Surirelloideæ are usually understood to include the genera Surirella, Podocystis, Cymatopleura and Campylodiscus, all of which resemble each other more or less, either in having a keel or markings like the divisions of the keel in Surirella and a median line, or pseudoraphe. The genus Nitzschia also has a keel, but it does not border each side of the valve as in Surirella, being found either near one margin or between it and the centre. Certain of the Surirellæ are allied to the group Tryblionella of the Nitzschiæ, while forms of Stenopterobia are distinguished with difficulty from the group Sigmata.

The following arrangement, therefore, is intended to include all genera having a keel or something which resembles it.

Hantzschia.--Valve asymmetrical; keels of the two valves opposite each other.

Nitzschia.--Valve asymmetrical; keels not (usually) opposite each other.

Surirella.--Valve usually symmetrical; a keel on each border.

Cymatopleura.--Valve without an elevated keel, but with markings like those of Surirella; undulated in zone view.

Campylodiscus.--Valves saddle-shaped.

HANTZSCHIA GRUN. (1877)

(named after C. A. Hantzsch)

Valve arcuate, with rostrate ends; keel puncta short, prolonged into costæ or extending across the valve; median nodule rudimentary; the keels of the two valves opposite each other.

Distinguished from Nitzschia chiefly by the position of the keels. According to Mereschkowsky, however, two species of Nitzschia, N. lanceolata and N. spectabilis, show the same peculiarity.

Chromatophores four, two on each of the zones (Mereschkowsky).

HANTZSCHIA AMPHIOXYS (EHR.) GRUN.

Valve slightly arcuate, with rostrate apices; keel puncta, 8 in 10 µ; striæ transverse, 16-18 in 10 µ, punctate. L. 60 µ.

Quite variable.

Fresh water.

Pl. 32, Fig. 9.

{114}HANTZSCHIA AMPHIOXYS VAR. MAJOR GRUN.

Valve as in type, but the keel puncta are 5 in 10 µ and the striæ are 11-12 in 10 µ. L. 71 µ.

H. amphioxys var. major Grun. is stated to be 120 µ in length. The present form is smaller but corresponds in puncta and striation. Van Heurck remarks that it approaches H. virgata.

Abundant in sand ripples on the beach at Cape May, N. J.

Pl. 39, Fig. 4.

Fig. 6, Pl. 39, is drawn from an authentic specimen of Wm. Smith's Nitzschia amphioxys, from England, and is introduced for comparison. The central nodule is not evident.

Fig. 3, Pl. 39, is from a specimen from an unknown locality. The keel puncta are 6 and the striæ 16 in 10 µ.

HANTZSCHIA VIRGATA (ROPER) GRUN.

Valve arcuate on the dorsal side, nearly straight on the ventral side, with rostrate, recurved apices; keel puncta prolonged to one-third the width of the valve, 4 in 10 µ; transverse striæ, 9-10 in 10 µ. L. 115 µ.

Shark River, N. J. (Kain).

I have not been able to find this form on our coast. The figure is drawn from a specimen from another locality.

Pl. 32, Fig. 23.

HANTZSCHIA MARINA (DONK.) GRUN.

Valve with dorsal margin slightly arcuate, ventral margin straight; apices rostrate and recurved; keel puncta, 6 in 10 µ, prolonged into costæ across the entire valve; transverse striæ, 12 in 10 µ, in double rows of alternating puncta between the costæ. L. 106 µ.

Epithemia marina Donkin.

Along the coast.

Pl. 32, Fig. 22.

NITZSCHIA HASSALL (1845), em. GRUN. (1880)

(named after Christian L. Nitzsch, of Halle)

Frustules usually free, sometimes enclosed in tubes or united into a filament. Valves keeled, the keels of the two valves usually diagonally opposite (see Hantzschia); keel puncta short or prolonged.

According to Mereschkowsky, there are at least two endochrome plates placed transversely on the zones; sometimes there are from four to six plates, in one species twenty granules and in another no trace of any endochrome whatever.

The following analysis is that of Grunow as given in Cleve and Grunow's "Arctic Diatoms," and adopted and illustrated by Van Heurck in his "Synopsis."

GROUPS

1. Tryblionella.--Keel very excentric, valve often folded; keel puncta indistinct, usually the same in number as the striæ.

2. Panduriformes.--Valve broad, constricted in the middle, with more or less evident fold; keel very near the edge; keel puncta quite evident or apparently wanting.

{115}3. Apiculatæ.--Keel very near the edge; valve linear or somewhat narrower in the middle; striæ on the longitudinal fold fainter than on the remaining surface, or wanting; puncta not in quincunx.

4. Pseudo-Tryblionella.--Keel more or less close to the edge; valve with a more or less deep longitudinal fold over which the striæ are spread in the same way as over the remaining surface; keel puncta always distinct.

5. Circumsutæ.--Valve with more or less wide longitudinal fold; keel very excentric; keel puncta quite evident; surface of valve irregularly punctate and also traversed by rows of delicate puncta which belong to a different layer of the valve.

6. Dubiæ.--Like the group Pseudo-Tryblionella, but the valves are not so much folded; frustules sometimes narrowed in the middle. The separation of species is difficult and, in part, doubtful. Keel excentric.

7. Bilobatæ.--Like the group Dubiæ, but with more central keel and so forming a transition to the group Pseudo-Amphiprora; valves without longitudinal folds.

8. Pseudo-Amphiprora.--Valve with quite central, sharp keel, arcuate, without longitudinal fold; keel puncta always evident; frustule narrowed in the middle with more or less marked central nodule.

Includes two species not found in this locality.

9. Perrya.--Valve arched with very sharp central keel; not narrowed in the middle; keel puncta mostly on short or long lines which are sometimes interrupted.

Includes six species not found in this locality.

10. Epithemioideæ.--Keel excentric; keel puncta extended into costæ across the entire valve.

11. Grunowia.--As in the group Epithemioideæ, except that the costæ are shorter, not extending across the valve; keel very excentric.

12. Scalares.--Like Grunowia, but with sharper, somewhat excentric keel; transverse section of frustule quadrangular.

13. Insignes.--Like Scalares, but with more central keel so that many of the forms are near the group Perrya; frustule somewhat sigmoid.

14. Bacillaria.--Keel central or nearly so; valve somewhat arched; keel sharp, as in the group Insignes.

15. Vivaces.--Keel moderately excentric; valve, according to position, semi-lanceolate, with keel puncta in short rows, or lanceolate with quite central keel. The valves have in many positions a resemblance to Hantzschia, so that N. vivax frequently becomes confounded with a form of H. amphioxys. The median keel puncta are not distant and a central nodule is not evident as is the case in all species of Hantzschia.

16. Spathulatæ.--Like the group Bacillaria, but usually with very delicate striated valves; keel in valve view usually bordered with two parallel lines.

17. Dissipatæ.--Like Vivaces and Spathulatæ, but with smaller central keel and without parallel lines. Valves usually small, very delicately striated; no central nodule.

18. Sigmoideæ.--Keel quite central; no parallel lines; frustule sigmoid; valve without longitudinal furrow; keel puncta not extended; no central nodule evident.

19. Sigmata.--Like Sigmoideæ, but with a more excentric keel.

20. Obtusæ.--Like Sigmata, with a more or less excentric keel which has in the middle a small bending to the inside; middle keel puncta somewhat more distant than the others, and between them a central nodule evident.

{116}21. Spectabiles.--Valve large, slightly arcuate, with excentric keel; no longitudinal folds; keel puncta somewhat extended over the valve but much less than in the group Insignes, and often scarcely perceptible.

22. Lineares.--Keel somewhat excentric, but less than in Spectabiles; frustule straight, sometimes a little constricted in the middle, so that a transition is shown to the groups Dubiæ and Bilobatæ. Valve without longitudinal fold; keel puncta round or somewhat angular, scarcely extended.

23. Lanceolatæ.--Valve lanceolate, linear-lanceolate or rarely elliptical, with very excentric keel; not folded; keel puncta not extended.

24. Nitzschiella.--Valve with excentric keel and long, produced apices.

TRYBLIONELLA

NITZSCHIA TRYBLIONELLA HANTZSCH

Valve elliptical-lanceolate, with subacute apices; longitudinal fold well marked; striæ coarse, transverse, 5 in 10 µ; indistinct puncta intermediate between the striæ. L. 45 µ. Quite variable.

Blue clay.

Pl. 32, Fig. 8.

NITZSCHIA GRANULATA GRUN.

Valve elliptical or elliptical-lanceolate; striæ in double rows, each row of three or four small puncta along the margin and rows of large puncta about 6 in 10 µ across the valve. L. 28-44 µ.

Blue clay. Along the coast.

Pl. 32, Fig. 3.

NITZSCHIA NAVICULARIS (BRÉB.) GRUN.

Valve elliptical-lanceolate, with acute apices; striæ on one side a double row of large and small puncta, and on the other side radiate short rows of large puncta, 7 in 10 µ; middle of valve hyaline. L. 35-60 µ.

Blue clay. Not common.

Pl. 32, Fig. 4.

NITZSCHIA COMPRESSA (BAIL.)

Valve elliptical-lanceolate, sometimes acuminate; striæ, 6 or 7 in 10 µ, coarsely punctate. L. 56 µ.

Pyxidicula compressa Bailey.

Nitzschia punctata (Wm. Sm.) Grun.

Tryblionella punctata Wm. Sm.

Common along the coast.

Pl. 39, Fig. 7.

Var. minor (H. L. Smith).--Valve acuminate; striæ, 8 in 10 µ. L. 22 µ.

Pyxidicula compressa var. minor H. L. Smith, Type Slide No. 431.

Pl. 39, Fig. 8.

The smaller forms occur northward, while the larger are found southward. This is unquestionably Bailey's form, as indicated by his figure and by the fact that it is found everywhere along the coast. Wm. Smith's T. punctata is the same species, although the puncta are smaller.

{117}PANDURIFORMES

NITZSCHIA PANDURIFORMIS GREG.

Valve elliptical, constricted in the middle, with sub-cuneate apices; longitudinal fold, with a punctate longitudinal line; striæ transverse and oblique, 15 in 10 µ; keel puncta, 6 in 10 µ. L. 108 µ.

Along the coast. More often found southward.

Pl. 39, Fig. 2.

NITZSCHIA PANDURIFORMIS VAR. MINOR GRUN.

Valve elliptical, constricted in the middle, with cuneate apices; keel puncta, 9 in 10 µ; striæ in transverse and oblique lines about 20 in 10 µ; longitudinal fold bordered by a punctate line. L. 34 µ.

Pavonia, N. J., artesian well.

Pl. 32, Fig. 5.

The var. continua Grun. is reported as occurring in Shark River. It varies in having the longitudinal fold punctate. It is also usually smaller than var. minor.

APICULATÆ

NITZSCHIA APICULATA (GREG.) GRUN.

Valve oblong-linear, with cuneate-apiculate apices; striæ punctate, apparently interrupted or pervious, about 18 in 10 µ. L. 26 µ.

Chester River, Md.

Pl. 32, Fig. 6.

The puncta are continued across the valve, but are less distinct on the fold. The figure shows the entire frustule with the fold on each valve. The valves are sometimes slightly constricted.

NITZSCHIA ACUMINATA (WM. SM.) GRUN.

Valve linear, sometimes slightly constricted in the middle, with acuminate apices; longitudinal fold entirely without or with indistinct striæ; keel puncta not evident; striæ, 14-15 in 10 µ. L. 82 µ.

Port Penn, Delaware River.

Pl. 32, Fig. 13.

NITZSCHIA PLANA WM. SM.

Valve linear; apices acute, slightly constricted in the middle; longitudinal fold further from the keel than the margin, broad, with scattered puncta; striæ subtle, irregular, interrupted, about 18 in 10 µ; keel puncta oblong, 3-6 in 10 µ. L. 100-170 µ.

Blue clay. Along the coast.

Pl. 32, Fig. 2.

{118}PSEUDO-TRYBLIONELLA

NITZSCHIA LITORALIS VAR. DELAWARENSIS GRUN.

Valve linear, with obtusely rounded cuneate ends, scarcely, if at all, constricted in the middle; longitudinal fold wide; keel puncta, 5 or 6 in 10 µ, sometimes confluent; striæ obscure, about 21 in 10 µ. L. 75 µ.

Delaware River.

Pl. 32, Fig. 12.

This form is drawn from a slide of Christian Febiger containing an abundance of specimens from Delaware City, and marked "Nitzschia dubia."

CIRCUMSUTÆ

NITZSCHIA CIRCUMSUTA (BAIL.) GRUN.

Valve elliptical, sometimes more than 200 µ in length; longitudinal fold more or less conspicuous; keel puncta about 4 in 10 µ, the middle distant with the appearance of a nodule; striæ irregular, subtle, finely punctate, frequently interrupted.

Surirella circumsuta Bail.

Tryblionella scutellum Wm. Sm.

Common in brackish water.

Pl. 32, Fig. 1.

DUBIÆ

NITZSCHIA DUBIA WM. SM.

Valve linear, scarcely, if at all, constricted in the middle, with cuneate, produced, apiculate apices, somewhat recurved; keel very excentric; puncta sometimes partly prolonged, about 9 in 10 µ; striæ, 20-24 in 10 µ. L. 93 µ.

Reported from along the New Jersey coast. I have not seen it. It is generally regarded as fresh-water. Slides sometimes labelled N. dubia are in reality N. litoralis var. delawarensis.

Pl. 39, Fig. 5.

The figure is drawn from a specimen from another locality.

BILOBATÆ

NITZSCHIA BILOBATA WM. SM.

Valve linear-lanceolate, constricted in the middle, apiculate at the ends; keel puncta 6 in 10 µ, prolonged unequally across part of the valve, the two median sub-remote; striæ, 16 in 10 µ. Frustule oblong, truncate, constricted in the middle. L. 120 µ.

Shark River, N. J., Chester River, Md.

Pl. 32, Figs. 10 and 11.

EPITHEMIOIDEÆ

NITZSCHIA EPITHEMIOIDES GRUN.

Valve linear, with cuneate, rostrate apices; slightly constricted on the keel side; keel puncta, 8 or 9 in 10 µ, extending as costæ across the valve; striæ delicate, 22 in 10 µ. L. 47 µ.

Brackish water, Long Island Sound.

Pl. 32, Fig. 21.

{119}GRUNOWIA

NITZSCHIA TABELLARIA GRUN.

Valve rhomboidal, inflated in the middle; apices produced; keel puncta extend in costæ across half of the valve, 7 in 10 µ; striæ transverse, about 22 in 10 µ. L. 20 µ.

Dimerogramma sinuatum Thwaites.

Nitzschia sinuata var. tabellaria (Grun.) V. H.

Schuylkill River. Not common.

Pl. 32, Fig. 7.

SCALARES

NITZSCHIA SCALARIS (EHR.) WM. SM.

Valve linear, with obtusely conical apices; costæ transverse, extending more or less to one-third the width of the valve, 3 or 4 in 10 µ; striæ, 9 or 10 in 10 µ, punctate. Length of valve quite variable, up to 480 µ (Cleve).

A well-known form, abundant in salt marshes and more or less brackish water.

Pl. 33, Fig. 6. (To the right of the figure is an outline of the valve reduced one-third.)

INSIGNES

NITZSCHIA INSIGNIS GREG.

Valve nearly linear or linear-lanceolate; apices broad, slightly produced, obtuse; keel puncta extended into short costæ, 4 or 5 in 10 µ; striæ about 14 in 10 µ. Length variable up to 400 µ.

Delaware Bay.

Pl. 33, Fig. 8.

BACILLARIA

NITZSCHIA PAXILLIFER (O. F. MUELLER) HEIBERG

Frustules united in a filament, afterwards free; valve lanceolate with nearly central keel; keel puncta, 7-9 in 10 µ; striæ about 21 in 10 µ. L. 110 µ.

Vibrio paxillifer O. F. Mueller.

Bacillaria paradoxa Gmelin.

Nitzschia paradoxa (Gmelin) Grun.

Brackish water or streams subject to its influence.

Pl. 33, Figs. 13 and 14.

Otto Frederick Mueller, in 1786, published at Copenhagen a work on "Infusorial Animalcules," including a description of a Vibrio which he named paxillifer, obviously alluding to the partially-extended frustules bearing at the end a tablet-like bundle. Two years later, Gmelin described the same form as Bacillaria paradoxa, a name still used. Heiberg, however, in 1863, placed the form under Nitzschia where it properly belongs and called it Nitzschia paxillifer (O. F. Mueller). I have adopted Heiberg's name.

Perhaps the most remarkable of all diatoms. Many species possess the power of motion, which, however, is evident only in the free frustule. In N. paxillifer, the movement of the frustules occurs without the loss of continuity or adherence to each other, so that, while at one time the adnate frustules form a narrow filament, like that of Fragilaria, at another {120}time they move laterally to their extreme length and form a thread of frustules adherent at their ends, later resuming their original position. The motion is repeated at intervals of from five to ten seconds. No satisfactory explanation of the movement has ever been made. In the filamentous form the frustules adhere to water-plants.

VIVACES

NITZSCHIA FLUMINENSIS GRUN.

Valve lanceolate, apices produced; keel puncta, 4-6 in 10 µ, partly extended in short costæ; striæ transverse, 14-15 in 10 µ, punctate; keel without a pseudo-nodule. L. 73 µ.

Common at Greenwich Point, Philadelphia.

Pl. 32, Fig. 16.

The form here figured is smaller than the type, which is from 130-160 µ in length.

SPATHULATÆ

NITZSCHIA SPATHULATA BRÉB.

Frustule linear, truncate, dilated at the ends; zone with longitudinal folds; valve lanceolate, keel central; apices acute, with an elevated appendage; keel puncta, 5-6 in 10 µ; striæ very fine. L. 56 µ.

Atlantic City and Cape May, N. J. (Lewis).

Pl. 40, Fig. 3.

DISSIPATÆ

NITZSCHIA DISSIPATA (KUETZ.) GRUN.

Valve lanceolate, with sub-rostrate apices; keel excentric; keel puncta about 6 in 10 µ; striæ, 14 in 10 µ. L. 20-40 µ.

Fresh and brackish water.

Pl. 40, Fig. 7.

SIGMOIDEÆ

NITZSCHIA MACILENTA GREG.

Frustule sigmoid, truncate at the ends; valve linear, with sub-acute apices and nearly central keel; keel with 5-6 puncta in 10 µ; striæ obscure, about 25 to 28 (?) in 10 µ. Length variable, up to 490 µ.

As the valve is usually seen when the keel is on the margin, the outline (reduced one-third, shown to the left of the figure) is, as a rule, sigmoid.

Delaware Bay.

Pl. 33, Fig. 7.

NITZSCHIA VERMICULARIS (KUETZ.) HANTZSCH

Valve linear, sigmoid, attenuated toward the obtuse ends; keel puncta, 9 in 10 µ, quite distinct; striæ very fine. L. 105 µ.

Fresh-water pools.

Pl. 32, Fig. 24; Pl. 33, Fig. 9.

{121}SIGMATA

NITZSCHIA SIGMA (KUETZ.) WM. SM.

Frustule linear, sigmoid; valve linear, slightly sigmoid, tapering to the sub-acute apices; keel excentric, puncta, 8 in 10 µ; striæ, 20-24 in 10 µ. L. to 250 µ.

Along the coast.

Pl. 39, Fig. 13.

NITZSCHIA SIGMATELLA GREG.

Valve linear, sigmoid, slightly attenuated toward the obtuse apices; keel excentric, puncta, 8-10 (?) in 10 µ; striæ delicate, 25-30 in 10 µ. L. to 400 µ. The keel puncta are quite obscure.

Nitzschia curvula Wm. Sm.

Nitzschia sigma var. curvula (Wm. Sm.) De Toni.

Fresh water. Hammonton Pond; May's Landing, N. J.

Pl. 33, Figs. 4 and 5.

Gregory remarks that the keel puncta are seen in some specimens. In both of the forms figured I have counted 30 striæ in 10 µ, but, after many examinations, I have not been quite certain about the keel puncta. The general appearance of the valves in any position is that of a Stenopterobia or Surirella anceps, with which it occurs.

NITZSCHIA CLAUSII HANTZSCH

Valve linear, slightly sigmoid, tapering to the sub-capitate ends; keel puncta, 11 in 10 µ; striæ subtle. L. 40 µ.

Abundant in Ridley Creek, Delaware Co. (Palmer).

Pl. 32, Fig. 20.

OBTUSÆ

NITZSCHIA OBTUSA WM. SM.

Frustule sigmoid, rounded at the ends; keel somewhat excentric, inflexed in the middle, the two median puncta distant; keel puncta, 5-6 in 10 µ; striæ, 26 in 10 µ. L. to 300 µ.

Along the coast.

Pl. 39, Fig. 16.

NITZSCHIA OBTUSA VAR. FLEXELLA H. L. SMITH

Valve more attenuate at the ends than the type and smaller.

Pl. 39, Fig. 14.

NITZSCHIA OBTUSA VAR. SCALPELLIFORMIS GRUN.

Valve linear, with apices unilaterally truncate; keel excentric; keel puncta, 8 in 10 µ; striæ, 26 in 10 µ. L. 48 µ.

Along the coast.

Pl. 32, Fig. 17.

{122}SPECTABILES

NITZSCHIA SPECTABILIS VAR. AMERICANA GRUN.

Frustule linear, slightly constricted in the middle, with sub-cuneate ends; valve linear, slightly arcuate, tapering to the sub-rostrate ends; keel excentric, keel puncta sometimes confluent, 4-6 in 10 µ, prolonged into short costæ; striæ distinct, 14 in the middle, 18 at the ends in 10 µ (but variable in different specimens). L. 186 µ.

Blue clay, especially at Tioga St.

Pl. 33, Fig. 3; Pl. 39, Fig. 1.

This is, probably, one of the most beautiful of the Nitzschiæ. It sometimes, according to De Toni, reaches a length of 520 µ.

Grunow states that his variety is found in the S. Bridgeton deposit. In a slide of Moeller labelled "Bridgeton, Maine," I find specimens identical in every respect with the Philadelphia form.

LINEARES

NITZSCHIA LINEARIS (AG.) WM. SM.

Valve linear, slightly inflexed in the middle; keel excentric; keel puncta, 8-9 in 10 µ, the two median distant; striæ about 30 in 10 µ. Frustules in zone view narrowed toward the ends, truncate. L. 75 µ.

Very common in fresh water.

Pl. 32, Fig. 18. Fig. 20, Pl. 40, a transverse section of frustule.

LANCEOLATÆ

NITZSCHIA PALEA (KUETZ.) WM. SM.

Valve linear-lanceolate, slightly rostrate at the apices; keel puncta, 10 in 10 µ, the median not distant; striæ, 33-36 in 10 µ; zone view linear, with rounded ends. L. 25-65 µ.

Fresh water.

Pl. 32, Fig. 15.

NITZSCHIA AMPHIBIA GRUN.

Valve lanceolate, apices sometimes slightly produced, rounded; keel puncta, 8-9 in 10 µ; striæ, 16 in 10 µ. L. 20-32 µ.

Fresh water.

Pl. 32, Figs. 14 and 25.

NITZSCHIA COMMUNIS RAB.

Frustule linear, slightly attenuated at the obtuse ends; valve elliptical-lanceolate, attenuated toward the obtuse ends; keel puncta, 12 in 10 µ; striæ more than 30 in 10 µ. L. 35 µ.

Fresh water.

Pl. 32, Fig. 19.

NITZSCHIA INTERMEDIA HANTZSCH

Valve linear-lanceolate; keel puncta, 8 in 10 µ; striæ about 24 in 10 µ. L. 100 µ.

Crum Creek. Not common.

Pl. 33, Fig. 2.

{123}NITZSCHIELLA

NITZSCHIA LONGISSIMA (BRÉB.) RALFS

Valve linear-lanceolate, with exceedingly long horns or beaks; keel puncta about 10 in 10 µ; striæ about 16 in 10 µ. L. to 500 µ.

Shark River, N. J.

Pl. 33, Fig. 1.

Forma parva V. H.--Keel puncta, 10-12 in 10 µ. L. 70 µ.

East Park Reservoir, Philadelphia.

Pl. 33, Fig. 10.

Differs from N. closterium (Ehr.) Wm. Sm. in the keel puncta.

The type form occurs in brackish and salt water. The occurrence of the variety in fresh water is another instance of the finding of presumably brackish forms in the water supply of the city. If these cases prove to be unusual, it may be because of one of two reasons. The Schuylkill River, before the building of the dam at Fairmount, was tidal as far as the Falls of Schuylkill, and brackish influences, while not now existent, may have caused the growth of forms which now survive. Another reason may be that the opening of the locks at Fairmount Dam may cause a slight admission of brackish forms from tidal water below. The abundance of the brackish species appears to indicate that the first reason is the more plausible.

NITZSCHIA REVERSA WM. SM.

Valve lanceolate extended into beaks or horns curving in opposite directions; keel puncta not evident; striæ, "20-26" in 10 µ. L. 70 µ.

Brackish water. Abundant in Duck Creek, Delaware River.

Pl. 33, Fig. 11.

NITZSCHIA ACICULARIS (KUETZ.) WM. SM.

Valve lanceolate, with beaks or horns about half the length of the median part of the valve; keel puncta, 18 in 10 µ; striæ exceedingly delicate, "about 40 in 10 µ." L. 45 µ.

Fresh water. Darby Creek.

Pl. 33, Fig. 12.

HOMOEOCLADIA AG. (1827)

(homoios, like, and clados, a branch)

Frustules like Nitzschia, but enclosed in branching or simple tubes.

HOMOEOCLADIA FILIFORMIS WM. SM.

Frustule linear, tumid in the middle, obtuse at the ends; valve linear-lanceolate, with somewhat acute apices; keel central or nearly so; keel puncta, 8 in 10 µ; striæ delicate. L. 108 µ.

Fresh and brackish water. Newark, N. J.

Pl. 33, Fig. 15.

{124}SURIRELLA TURPIN (1828)

(named after Dr. Suriray, a physician of Havre)

Valve linear, elliptical or ovate; pseudoraphe linear or lanceolate; a marginal keel forming wings or alæ seen in zone view; costæ short or reaching the pseudoraphe, frequently with intercostal striæ more or less evident.

The genus is divided by Grunow according to the length and form of the costæ. I include Stenopterobia.