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.
(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.)
(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.
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.
(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.
(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.
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.
(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.
(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.
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).
(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.).
(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 BŒCKII (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.
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. bœckii.
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.)
(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.
ANOMŒONEIS 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.
ANOMŒONEIS 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.
ANOMŒONEIS 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.
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.
(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. 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.
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.
(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.
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.
(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.