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.
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.
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.
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.
(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.
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.
(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.
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.
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.
(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.
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.
(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.
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.
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.
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.
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.