SPECIES starting with "N"

Symmetrical biraphid - Navicula aitchelbee has lanceolate valves 20-36 μm long with subcapitate apices. The central area is small and asymmetric. Striae number 14-16 in 10 μm and are straight near the central area.

Symmetrical biraphid - Valves are linear with slightly protracted ends. The central area is larger on the primary side, and semi-elliptical and smaller on the secondary side, but in some specimens it may be nearly symmetrical. Striae are radiate at the central valve, convergent near apices Striae are 11-12 in 10 µm. Areolae are lineolate, with approximately 32 in 10 µm.

Symmetrical biraphid - Navicula antonii is characterized by its lanceolate shape and curved striae. The axial area is narrow, widening only slightly at the central area. The central area is often irregular but may be distinctly ovate.

Symmetrical biraphid - Navicula aurora has large elliptic-lanceolate valves. Valve ends are broadly rounded and slightly protracted. The central area is transversely rectangular with rounded margins. Proximal raphe ends are triangular and deflected slightly toward the secondary side. Terminal striae are straight, not bent.

Symmetrical biraphid - Valves are small and lanceolate with protracted apices. The central area is asymmetrical. It is barely differentiated from the axial area on one side of the valve, but enlarged on the other side. The striae are lineolate, composed of areolae that are distinct in LM. The proximal raphe ends are unilaterally deflected; distal raphe fissures are hooked. The striae are radiate at the center and parallel, or convergent, at the apices. The space between each stria is more broad than the width of the stria.

Symmetrical biraphid - Valves are lanceolate with distinctly protracted, rostrate ends.

Symmetrical biraphid - Navicula cari has lanceolate to linear-lanceolate valves with a distinct, rounded to rectangular central area. Striae are evenly spaced throughout and both curved and strongly radiate near the valve center.

Symmetrical biraphid - Navicula caroliniae has broadly lanceolate valves 23-41 μm long with obtusely rounded to subcapitate apices. Striae number 11-14 in 10 μm and are evenly spaced throughout the valve. Areolae number 24-28 in 10 μm.

Symmetrical biraphid - Valves are lanceolate with protracted, subrostrate ends. The central area is small. Striae are radiate in center and parallel to slightly convergent at the apices, 18-20 in 10 µm. Striae may be bent in the middle of the valve. Short striae may alternate with longer ones around the central area.

Symmetrical biraphid - Navicula cincta has linear-lanceolate to elliptic-lanceolate valves with unprotracted apices. The central area is small and irregular in shape. Striae are irregularly shortened and more widely spaced in the central area.

Symmetrical biraphid - Valves are lanceolate with protracted apices The central area is large and circular. The raphe is straight, with 'drop-like' expanded external proximal ends. Striae are radiate around the center, becoming convergent at the apices. The areolae are sometimes visible under LM, approximately 35 in 10 μm.

Symmetrical biraphid - Navicula cryptocephaloides has lanceolate valves with acutely rounded and weakly protracted apices. The proximal raphe ends are straight. The central striae are radiate and straight and areolae in the striae are relatively coarse and easily resolved in LM.

Symmetrical biraphid - Navicula cryptofallax is a small Navicula with lanceolate valves and narrow rostrate to subcapitate apices. The central area is small and variable in shape with irregular margins. Proximal raphe ends are weakly expanded and the striae are strongly radiate near the center of the valve.

Symmetrical biraphid - Navicula detenta has elliptic valves less than 8 µm wide. Apices are rostrate to subcapitate. The central area is linear in the apical axis and striae are usually complete about the central area.

Symmetrical biraphid - Navicula duerrenbergiana has weakly silicified frustules that are easy to overlook in strewn mounts. Valves are narrow linear-lanceolate with pointed apices. The striae are finely lineate and weakly radiate throughout. The proximal raphe ends are very close and not expanded. Central area is absent.

Symmetrical biraphid - Valves are lanceolate and 21-36 µm long by 5-7 µm wide. The central raphe ends are deflected and the central area is asymmetric.

Symmetrical biraphid - Valves are robust, linear-elliptical with broadly rounded or wedge-shaped apices. The lineolate striae are composed of coarse, distinct areolae. The central area is prominent and asymmetrically rounded. Valves are 6.1-9.1 µm wide.

Symmetrical biraphid - Navicula flatheadensis has large lanceolate valves that are wider than 10 microns. Valve apices are relatively wide, weakly protracted, and rounded. The proximal raphe ends are distant and deflected to the primary side. The central nodule is typically asymmetric with one flat side and one convex side. Terminal striae become parallel and then weakly convergent at the valve apices.

Symmetrical biraphid - Valves are strongly lanceolate, with narrow, attenuated ends. The asymmetric central area is distinct. Striae are linear and radiate at the center to weakly convergent at the apices. Striae are coarse and distinct; they are more widely spaced at the central area (5 in 10 µm) than the rest of the valve (8–10 in 10 µm). The proximal raphe ends expand into a rounded terminal pore.

Symmetrical biraphid - Navicula galloae has narrow lanceolate valves with rounded apices, 12-14 µm wide. The central area is roundish, but asymmetric. Areolae number 24 in 10 µm. External proximal raphe ends are recurved.

Symmetrical biraphid - Valves are lanceolate with drawn-out apices, 32-39 µm long, 7.0-8.3 µm wide. The central area is slightly asymmetrical, elliptical. The raphe is straight, with external proximal raphe endings slightly dilated and bent towards primary side of the valve. The central nodule is asymmetrically expanded on the internal valve surface to the primary side. Striae are radiate around the center, 13-15 in 10 µm, becoming parallel then convergent at the apices.

Symmetrical biraphid - Valves are linear-lanceolate. The central area is strongly asymmetrical; wedge-shaped on the primary side and semi-lunate on the secondary side. Striae are radiate in the central part of the valve and parallel near the apices. Striae are 9-10 in 10 µm. Proximal raphe ends are deflected toward the primary side.

Symmetrical biraphid - Valves are small (< 20 µm) and broadly lanceolate, with narrow, subrostrate apices. The central area is rectangular with a single, short stria on each side. The striae are slightly radiate and those near the central area are curved.

Symmetrical biraphid - Valves are lanceolate with protracted apices, 4.1-7.0 µm wide. The central area is asymmetric and elliptical. The external proximal raphe ends are sharply bent toward primary side of the valve. Striae are slightly radiate around the center, numbering 14-18 in 10 µm and are convergent at the apices. The areolae are clearly visible under LM, numbering 25-32 in 10 μm.

Symmetrical biraphid - Valves are linear to elliptic-linear, with narrowing rounded apices. The “H-shaped” hyaline area immediately adjacent to the axial area is narrow, with a single areola associated with each stria. The axial area is curved and elevated from the valve face, with a disruption between the proximal raphe ends. The proximal raphe ends are tear-drop shaped. There is a fine hyaline line extending along the valve margin from apex to apex. Only 3–5 areolae comprise the stria from the valve margin to the hyaline “H-shaped” zone.

Symmetrical biraphid - Valves lanceolate with rounded ends. Striae radiate through most of the valve, becoming convergent at the ends. Central area is a somewhat rounded rectangle, or it may be square or irregular (asymmetric).

Symmetrical biraphid - Navicula leptostriata has narrowly lanceolate valves with a small central area. Proximal raphe ends are deflected to the primary side and are positioned close to one another. Striae are 18-20 in 10 µm, curved and radiate at the valve center and convergent at the apices.

Symmetrical biraphid - Valves are lanceolate with rounded or very slightly drawn-out ends. The proximal raphe ends are straight and slightly expanded. The central area is transversely elliptical or irregular-rectangular, often slightly asymmetric. The lineolate striae are radiate, becoming convergent at the valve apices, 12-13 in 10 µm. The areolae are easily observed under LM and number 28-32 in 10 µm.

Symmetrical biraphid - Valves are linear with rostrate to capitate apices. The raphe is straight, with close proximal ends. Striae are strongly radiate around the center, becoming convergent at the apices. The areolae are indistinguishable under LM.

Symmetrical biraphid - Navicula ludloviana has very large valves with broad, finely lineate striae that are radiate throughout. The axial area widens considerably to a somewhat wider and orbicular central area. The raphe branches are distinctly bowed and the proximal ends are large and bulbous.

Symmetrical biraphid - Navicula lundii has lanceolate valves with unprotracted or slightly protracted apices. The central area is transapically expanded and asymmetric.

Symmetrical biraphid - Valves are lanceolate to linear-lanceolate with slightly drawn-out ends. Valves are 4.1-5.5 μm wide. Axial area is narrow, central area is small, rhomboid to elliptical. Proximal raphe ends are noticeably deflected to the primary side. Striae are radiate and bent at valve center, convergent at apices, 14-17 in 10 μm. There are 36-40 lineolae in 10 μm.

Symmetrical biraphid - Valves are large and broadly lanceolate with rounded apices. The central area is asymmetric and distinct. The axial area is wide and somewhat irregular. Striae are widely spaced and areolae distinct in LM. The proximal raphe ends expand into a rounded terminal pore slightly curved to one side. The distal raphe fissures are scythe-shaped.

Symmetrical biraphid - The large valves of Navicula oblonga are linear and lack protracted ends. Although terminal striae are convergent at the margins, they are bent back toward the central area and are radiate next to the axial area. Short central striae often do not reach the valve margins. Proximal raphe ends are simple and barely wider than the raphe. Striae are finely lineate and the individual areolae are difficult to distinguish.

Symmetrical biraphid - Navicula oppugnata has lanceolate valves, wider than 8 µm. Proximal raphe ends are bent to the secondary side of the valve. Striae are coarse and number 9-11 in 10 µm. Arolae are also coarse, easily resolved in LM and number 24-26 in 10 µm.

Symmetrical biraphid - Navicula peregrina has large, lanceolate valves, more widely spaced striae in the central area, relatively coarse areolae, expanded proximal raphe ends deflected to the primary side, and a preference for brackish water.

Symmetrical biraphid - Valves are linear to linear-lanceolate, with narrow rounded apices. The small asymmetric central area is distinct and the axial area is narrow. Striae are narrowly spaced except around the central area. Striae are coarse and number 10-12 in 10 µm. Lineate areolae are easy to observe. The proximal raphe fissures are expanded. The distal raphe fissures are scythe-shaped.

Symmetrical biraphid - Navicula piercei has long linear valves with a tumid center.

Symmetrical biraphid - Valves are lanceolate and 8-11 µm in width. Apices are narrow and protracted, except in small specimens. The striae near the apices are variable; they may be radiate or parallel. The striae near the center of the valve are straight, rather than bent.

Symmetrical biraphid - The valves are narrow and lanceolate with acutely rounded ends. The central area is rhombic. The striae are strongly radiate. Striae are bent in the valve center and convergent near the poles. Lineolae number 28-32 in 10 μm.

Symmetrical biraphid - Valve lanceolate with blunt, subrostrate ends. The central area is variable in shape, from circular to transversely rectangular. The raphe is straight, as are the proximal raphe ends.

Symmetrical biraphid - Valves are lanceolate with protracted, subrostrate ends. The central area is small. Striae are radiate in center and convergent at the apices, 14-16 in 10 µm. Areolae number 32-36 in 10 µm and are hardly distinguishable in LM. Striae are bent in the middle of the valve. Short striae often alternate with longer ones around the central area.

Symmetrical biraphid - Navicula reinhardtii has elliptical to oblong valves with wide, coarsely lineate striae, a transverse central area formed by alternating long and short striae, and proximal raphe ends that are straight, small and bulbous.

Symmetrical biraphid - Valves are lanceolate with elongate-protracted, rounded apices. The axial area is narrow, straight, widening to form an irregularly-rounded to elliptical central area. The central area formed by shortened striae that are also more widely spaced than elsewhere on the valve. The striae are distinctly lineate, radiate around the center, becoming parallel, then convergent at the ends.

Symmetrical biraphid - Navicula rhynchotella has broadly lanceolate valves, narrow, subcapitate to capitate apices, striae with coarse, widely spaced areolae, and a preference for water with elevated concentrations of dissolved solids..

Symmetrical biraphid - Valves are linear to linear-lanceolate with subrostrate apices. The central area is often slightly asymmetrical. The raphe is straight, with external proximal raphe ends slightly dilated and bent towards primary side of the valve. The central nodule is asymmetrically expanded on the internal valve surface to the primary side. Striae are radiate and bent around the center, 12-14 in 10 µm, becoming parallel, then convergent at the apices.

Symmetrical biraphid - Valves are broadly elliptical-lanceolate with produced, rostrate ends. The elliptical to elliptical-lanceolate central area is formed by alternating long and short striae in the center of the valve. The striae are lineate, radiate, arched, becoming parallel near the apices.

Symmetrical biraphid - Valves are linear elliptical with convex margins and capitate, rostrate or blunt apices. Specimens within a population may be irregular (asymmetrical) and are often variable in the shape of the apices. The axial area is narrow near the apices, becoming more broad near the central area. The central nodule is thickened and distinct. Each stria is composed of a single, elongate areola.

Symmetrical biraphid - Navicula schweigeri has lanceolate valves that measure 39-49 μm long by 7.5-8.6 μm wide. Apices are short and rostrate. The central area is small, lanceolate and bordered by irregularly shortened striae.

Symmetrical biraphid - Valves are 5-6 µm wide with robust striae that number 11-12 in 10 µm. Striae are radiate in the middle, becoming abruptly convergent near the apices. The central 1 or 2 striae are shortened.

Symmetrical biraphid - Valves are linear-elliptic to linear-lanceolate, with apices that are wedge-shaped in short specimens and more produced and subrostrate in longer specimens. The central area is transversely elliptic or irregularly rhomboid. External proximal raphe endis are dilated. The central nodule is symmetric. Striae are radiate in the valve center, more widely spaced around the central area and convergent at the apices. The areolae are visible under LM, approximately 25 in 10 μm.

Symmetrical biraphid - Navicula sovereignii has bulbous, laterally expanded proximal raphe ends, "worm-like" markings on the axial and central areas, a round central area, and straight terminal striae.

Symmetrical biraphid - Navicula staffordiae has narrowly lanceolate valves with acutely rounded apices. The central area is small, elliptic and asymmetric.

Symmetrical biraphid - Valves are lanceolate with protracted ends that are relatively narrow compared to the valve width. The striae are strongly radiate and widely spaced near the center of the valve. The transition between radiate and parallel striae is abrupt at the Voigt discontinuities. Areolae are very coarse and easily distinguished in LM.

Symmetrical biraphid - Navicula subconcentrica has lanceolate valves that are less than 11 µm wide. Valve ends are narrow and acutely rounded to subcapitate. The proximal raphe ends are nearly straight and relatively close together. The central nodule is typically symmetric with flat or slightly concave sides.

Symmetrical biraphid - Valves elliptic-lanceolate and relatively small in size. The axial area is thickened, and may appear raised above the valve face. Valves lack a distinct central area. Striae are punctate and areolae may be visible in LM.

Symmetrical biraphid - Valves are linear-lanceolate with subrostrate to capitate apices, 29-42 µm long, 7.5-8.9 µm wide. The central area is rounded and slightly asymmetrical. The raphe is straight, with external proximal raphe ends hooked towards the secondary side of the valve. Striae are radiate, becoming parallel, then convergent at the apices. The central striae are radiate and are straight or very slightly bent. The areolae are clearly visible under LM, approximately 24-25 in 10 μm.

Symmetrical biraphid - Valves are lanceolate to linear-lanceolate with protracted apices. The central area is round. Proximal raphe ends are straight and close. Striae are straight, slightly radiate around the center, becoming parallel then convergent at the apices. The areolae are clearly visible under LM, 23-26 in 10 μm.

Symmetrical biraphid - Navicula supleeorum has lanceolate valves with acutely rounded apices. Striae number 12-14 in 10 µm. Areolae may be resolved in LM and number 30-32 in 10 µm.

Symmetrical biraphid - Valves are relatively small and linear with narrow, rounded apices. The central area is asymmetrically rounded. Striae are fine and number 12-17 in 10 µm.

Symmetrical biraphid - Navicula trilatera has linear-lanceolate valves 4.5-5.5 µm wide. Apices are subrostrate and the central area is moderately large and irregular.

Symmetrical biraphid - Valves linear-lanceolate with wedge-shaped ends. Central area variable in shape, symmetrical, transversely rectangular or elliptical. Striae parallel, or nearly parallel throughout the valve except near the central area and poles.

Symmetrical biraphid - Navicula trivialis is characterized by its lanceolate shape and subrostrate ends. Its ovate central area is also diagnostic as are the striae which are radiate nearly to the poles.

Symmetrical biraphid - Valves are medium-sized and lanceolate with narrow, slightly protracted ends. Striae are radiate, irregularly shortened and more widely spaced in the valve center. Areolae are coarse.

Symmetrical biraphid - Valves are narrowly lanceolate with drawn-out subcapitate ends, 8.7-9.5 µm wide, 51-70 µm long. The central area is transversely elliptical. The striae are strongly radiate, bent in the middle of the valve and convergent at the apices, 10-12 in 10 µm. Areolae are 34-36 in 10 µm.

Symmetrical biraphid - Valves are lanceolate to linear-lanceolate with moderately protracted apices. The central area is transversely rectangular or elliptic. The raphe is straight, with drop-like external proximal ends. The striae are slightly radiate around the center, becoming convergent at the apices. The areolae are sometimes visible under LM, approximately 35 in 10 μm.

Symmetrical biraphid - Valves are linear-lanceolate and narrow, with very slightly protracted apices. The central area is small. Striae are strongly radiate around the center, becoming convergent at the apices. The areolae are indistinguishable under LM.

Symmetrical biraphid - Valves are lanceolate to linear-lanceolate with subrostrate apices. Central area is asymmetric; trapezoid on primary side, semi-circular on secondary side. External proximal raphe ends are slightly dilated and bent toward the primary side of the valve. The central nodule is asymmetrically expanded on the internal valve surface to the primary side. Striae are radiate in the valve center, becoming convergent at the apices.

Symmetrical biraphid - Valves are linear with wedge-shaped apices. The central area is asymmetric, trapezoid on primary side, semi-circular on secondary side. External proximal raphe ends are bent towards primary side of the valve. The central nodule is asymmetrically expanded to the primary side. Areolae are visible under LM, 22-26 in 10 μm.

Symmetrical biraphid - Valves are lanceolate, with broadly rounded apices. The raphe is straight and filiform. The external proximal raphe ends are slightly dilated and rounded. The distal raphe ends are hook-like. Striae are distinctly lineate and radiate along most of the valve, becoming parallel to convergent at the apices.

Symmetrical biraphid - Navicula walkeri has longitudinal shadow lines, hooked proximal raphe ends, large, lanceolate valves, and a round, asymmetric central area.

Symmetrical biraphid - Navicula weberi has elliptic-lanceolate to broadly lanceolate valves with obtusely rounded apices. The central area is rounded and asymmetric. Striae are radiate, convergent at the apices and number 9-10 in 10 μm. Areolae are coarse and number 24 in 10 μm.

Symmetrical biraphid - Navicula whitefishensis has large valves with narrow subcapitate apices. The valve width is up to 14.2 µm. Striae are strongly radiate, except near valve ends. The central area is nearly round and large, 6-8 µm in diameter. The proximal raphe ends are expanded.

Symmetrical biraphid - Navicula wildii has narrow lanceolate valves with gradually attenuated and obtusely rounded apices. Striae number 12-14 in 10 μm. Areolae are not visible in LM, but number 30-36 in 10 μm.

Symmetrical biraphid - Navicula winona has narrowly lanceolate valves with gradually attenuated, narrow subcapitate apices. Areolae are coarse and number 24-28 in 10 μm.

Asymmetrical biraphid - Valves are moderately dorsiventral, with arched dorsal margin and flat, or slightly convex, ventral margin. The axial area is narrow; it widens in the valve center to form a small lanceolate central area. The raphe is straight and weakly lateral, with external proximal ends and terminal fissures hooked to the dorsal side. Striae are radiate in the valve center, becoming convergent at the ends.

Symmetrical biraphid - Neidiopsis levanderi has linear and triundulate valves with a longitudinal hyaline line on each side. Proximal raphe ends are straight and not expanded.

Symmetrical biraphid - Neidiopsis wulffii has linear-elliptic valves without obvious marginal undulations. A longitudinal hyaline line is present on each side near the valve mantle. Proximal raphe ends are simple and deflected to the same side.

Symmetrical biraphid - Neidium bobmarshallensis has lanceolate valves, 14-18 µm wide. The central area is diagonal. Striae are also diagonal and number 13-15 in 10 µm. The proximal raphe ends are hooked in opposite directions.

Symmetrical biraphid - Neidium fogedii has lanceolate to linear-lanceolate valves, with subrostrate to subcapitate apices. Valves are 9-11 µm wide. Both the striae and the central area are oriented diagonally to the apical axis. Striae number 17-18 in 10 µm. Proximal raphe ends are deflected and recurved in opposite directions.

Symmetrical biraphid - Neidium undulatum has large elliptic-lanceolate valves, 82-110 µm long. The apices are subrostrate. The axial area is wide with a row of depressions along one side of both raphe branches. The central area is diagonal, with disorganized depressions near the margins. Striae are coarse and number 10-12 in 10 µm.

Nitzschioid - Valves are very lightly silicified. Apices are extremely long, narrow, and straight. At the center of the valve, the margins are nearly parallel. The striae are extremely fine.

Nitzschioid - Valves are linear to lanceolate with variably shaped apices. Fibulae are distinct and number 11-14 in 10 µm. The central fibulae are equidistant and number 23-25 in 10 µm.

Nitzschioid - Valves taper to bluntly rounded apices. Fibulae are distinct, 7-9 in 10 µm. The central nodule, evident as a wider space between two central fibulae, is present. Striae are characteristically prominent and distinctly punctate, and may be irregularly spaced.

Nitzschioid - The valve margin is constricted at the center. A central nodule is present and fibulae are variable in size.

Nitzschioid - Valve linear-lanceolate with strongly sigmoid, beaked ends. Raphe parallel to slightly sigmoid, positioned nearly in the middle of the valve. Fibulae are irregular in size and spacing, approximately 8-9 in 10 µm. Valves sigmoid in girdle view. Striae are not discernible.

Nitzschioid - Valves are broadly linear with concave, protracted margins. The valves are distinctly to slightly sigmoid, a shape produced by the ends being bent in opposite directions. The apices are narrowly rounded. The striae are barely visible.

Nitzschioid - The valve apices are curved in opposite directions. The striae are very fine and difficult to resolve in the LM. At the center, the valve is slightly concave.

Nitzschioid - Valves are linear, with cuneate to subrostrate apices. Keel excentric, with fibulae numbering 6-8 in 10 µm. Striae faintly visible to unresolvable.

Nitzschioid - Valves linear with rounded apices. Fibulae are relatively large. Striae are fine and number 32-38 in 10 µm.

Nitzschioid - Valves elliptical-lanceolate with short, rostrate, narrowly rounded apices. Fibulae small, but distinct and number 14-16 in 10 µm.

Nitzschioid - The canal raphe is prominent, and positioned slightly eccentrically. The raphe lacks a gap in the center at the proximal raphe ends. The fibulae are also distinct and regularly spaced. A conopeum is recognizable under LM as two parallel lines, each running longitudinally on either side of the canal raphe. Striae count is high (32-50 in 10 µm), so striae may not be visible in the light microscope.

Nitzschioid - Valves are delicate, narrow with parallel sides and capitate ends. Keel strongly eccentric. Striae are not resolvable in the light microscope.

Nitzschioid - Valves are delicate, narrowly lanceolate with apices rostrate and subcapitate. Keel strongly excentric. Striae are not resolvable in the light microscope.

Nitzschioid - The valves are generally linear but can also be slightly sigmoid, especially in smaller specimens. The central nodule is prominent. The fibulae are irregularly spaces and sized. At the central area, the fibulae are positioned slightly off of the valve margin.

Nitzschioid - Valves lanceolate with subcapitate to subrostrate apices. A large central nodule is present. Fibulae are small and number about 13 in 10 µm. Striae are indistinct.

Nitzschioid - Valves are linear to elliptical. Fibulae are large, with the middle one larger and more distinct than the others. Striae are parallel at the center of the valve, but arched near the poles, especially in smaller valves.

Nitzschioid - Valves are linear-lanceolate, to somewhat elliptical, apices obtuse-rostrate. Fibulae are small. Striae are parallel, fine.

Nitzschioid - Valves are linear to linear-lanceolate, with sides parallel, except the side bearing the keel which is concave in the center. Apices rounded, nearly capitate. A distinct central nodule is present. Striae are resolvable.

Nitzschioid - Valves are linear with margins straight, or slightly concave. Apices are protracted, narrow and narrowly rounded. Striae are not easily resolvable.