SPECIES starting with "P"

Symmetrical biraphid - Pinnularia divergentissima is striking in appearance because of the abrupt transition from extremely radiate to extremely convergent striae. Valves are linear to linear-lanceolate with subrostrate and obtusely-rounded apices. Raphe branches are filiform and the proximal raphe ends are small and close to one another.

Symmetrical biraphid - Valves are triundulate with the broadest portion in the middle. Apices are capitate. The axial area is broad and lanceolate, merging with a central transverse fascia.

Symmetrical biraphid - Valves are elliptical-lanceolate, with margins convex and apices protracted and rostrate. The central area is round central. Striae are indistinctly punctate, curved and radiate throughout the length of the valve.

Symmetrical biraphid - Valves are linear-lanceolate and large, greater than 110 µm in length. Striae are somewhat convergent and more widely spaced at the valve center. Areolae are distinct in LM and number 15-18 in 10 µm.

Symmetrical biraphid - Valves are lanceolate and less than 110 µm long. A prominent keel carrying the raphe runs along the apical axis. Striae are parallel in the middle, becoming radiate towards the apices. Areolae are very fine and number 26-30 in 10 µm.

Monoraphid - Valves are elliptic-lanceolate with subrostrate apices. The raphe valve has a transversely rectangular to elliptic central area. The rapheless valve has a rhomboid axial area and asymmetric central area with a hood on the internal valve surface. The striae are radiate.

Monoraphid - Valves are elliptical-lanceolate with apiculate apices. The raphe valve has a large rhomboid or transversely elliptical central area. The rapheless valve has an asymmetrical central area, expanded at one side to the valve margin and containing a prominent hood . The striae are strongly radiate on the raphe valve and slightly radiate on the rapheless valve.

Monoraphid - Valves are lanceolate with capitate to subrostrate apices, 12-25 μm long, 5.4-7.0 μm wide. Rapheless valve has a linear-lanceolate axial area and an asymmetrical central area containing a hood on the internal valve surface. The striae are multiseriate, radiate throughout both valves, 12-15 in 10 μm.

Monoraphid - Valves are elliptical. The axial area is narrow and linear on the raphe valve; the axial area is narrow and rhomboid on the rapheless valve. The central area on both valves is asymmetric, expanded to the valve margins and contains a hood. The striae are fine and radiate throughout both valves.

Monoraphid - Valves are lanceolate with protracted subrostrate apices. The raphe valve has a transversely elliptical or rectangular central area. The rapheless valve has a linear-lanceolate axial area and no distinguishable central area, or two middle striae on one side of the raphe can be slightly more distant for each other than from the other striae.

Monoraphid - Valves are linear-elliptical with rostrate, subrostrate or narrowly subcapitate apices. The raphe valve has a linear axial area and transversely rectangular central area. The rapheless valve has a narrow, linear axial area. The asymmetric central area on the rapheless valve contains a shallow depression on the internal valve surface.

Monoraphid - Valves are lanceolate to elliptical with rounded or slightly drawn-out apices, 5-17 μm long and 3-6 μm wide. The rapheless valve has a linear-lanceolate axial area that slightly widens in the middle. The asymmetrical central area on rapheless valve contains a hood on the internal valve surface.

Monoraphid - Valves are lanceolate to elliptical-lanceolate with capitate apices, 9-25 μm long, 4.8-7.0 μm wide. Small specimens have subrostrate, rather than capitate apices. The asymmetrical central area on the rapheless valve contains a rimmed depression on the internal valve surface. The striae are multiseriate, radiate throughout both valves, 14-15 in 10 μm.

Monoraphid - Valves are relatively large with slightly rostrate apices. The raphe valve has a distinct central area that is "bow tie" shaped. The rapheless valve has a large, broad central area, becoming more narrow toward the apices. Distal raphe ends are deflected to opposite sides of the valve.

Monoraphid - Valves are lanceolate to elliptical-lanceolate with slightly drawn-out apices, 7-24 μm long, 4.5-8.0 μm wide. The asymmetrical central area on rapheless valve contains a rimmed depression on the internal valve surface. The striae are multiseriate, radiate throughout both valves, 12-15 in 10 μm.

Monoraphid - Valves are elliptical with rostrate, subrostrate or narrowly subcapitate apices, 11.0-17.5 μm long, 5.0-6.0 μm wide. Rapheless valve has a linear axial area, which in some population considerably widens in the center. The central area on the rapheless valve is asymmetrical and contains a hood. The striae are multiseriate and radiate throughout both valves, 11-13 in 10 μm.

Monoraphid - Valves are elliptic. Raphe valve has a narrow linear axial area and a small central area. Raphe is filiform, straight, with slightly expanded distal and proximal ends. Rapheless valve has a linear–lanceolate axial area. Striae are multiseriate, radiate.

Monoraphid - Valves are linear-elliptical. The raphe valve has a narrow axial area and transversely rectangular central area that reaches valve margins. The rapheless valve has a lanceolate axial area and no distinct central area or the two middle striae may be slightly more distant from each other than other striae. The raphe is straight, with slightly expanded terminal and central ends, without terminal raphe fissures. Striae are almost parallel in the valve center, but become strongly radiate through both valves, biseriate, 12-16 in 10 µm.

Monoraphid - Valves are elliptical. The raphe valve has a narrow axial area and a transversely elliptical or rectangular central area. The rapheless valve has a wide lanceolate axial area and lacks a distinct central area.

Monoraphid - Valves are elliptic. Raphe valve has a narrow linear axial area and transversely rectangular central area. Raphe is filiform, straight with slightly expanded external distal and proximal ends. Striae are uniseriate and moderately radiate on the raphe valve (26-30 in 10 μm). The rapheless valve has a wide elliptic–lanceolate axial area and short triseriate striae (12-15 in 10 μm).

Monoraphid - Valves are elliptic. The raphe valve has a narrow linear axial area and a wide, bow-tie-shaped central area. The striae on the raphe valve are uniseriate and strongly radiate. The rapheless valve has a wide lanceolate axial area bordered by short and broad biseriate striae.

Monoraphid - Valves are elliptic. Both valves have a linear axial area. The central area on the raphe valve is transapically rectangular, often reaching valve margins. The central area on the rapheless valve is small and often asymmetric. Striae are radiate and biseriate. The stria density on both valves is 14-18 in 10 µm.

Centric - Valves circular to elliptical and 65–120 μm in diameter. Two ocelli positioned opposite one another. Two to three rimoportulae are present, each with a small hyaline area surrounding each. Spinules are present across valve face and at the margin.

Monoraphid - Valves are elliptical. Both valves have narrow axial areas, which are often oblique to the apical axis, not parallel between the two valves, and sigmoid toward the apices. The central area is transversely elliptical or rectangular. The striae are radiate throughout .

Monoraphid - Valves are linear-elliptical, often slightly gibbous at midvalve. Both valves have a linear axial area and transversely rectangular central area. The raphe is straight, without terminal raphe fissures. Striae are radiate on both valves, 27-33 in 10 µm, interrupted at the valve margin.

Monoraphid - Valves are elliptical to linear-elliptical. Valves very small, less than 10 μm in length. Both valves have small transversely elongated central areas. The raphe is straight, without terminal fissures. Striae are radiate on both valves, 27-31 in 10 µm.

Monoraphid - Valves are elliptical to linear-elliptical. The raphe valve has a linear axial area, which widens into a transapically elliptical, rectangular, or diamond-shaped central area. The raphe is straight without terminal raphe fissures. The rapheless valve has a large rhomboid axial area with an irregular border. The striae are radiate, 24-30 in 10 µm.

Monoraphid - Valves are linear-elliptical, slightly constricted in the middle. The raphe valve has a small circular or elliptical central area. The raphe is straight, without terminal fissures. The rapheless valve has a large rhomboid axial area. Striae are radiate on both valves and interrupted at the valve margin. Striae number 28-32 in 10 µm on raphe valve, 25-28 in 10 µm on rapheless valve .

Monoraphid - Valves are lanceolate with rostrate apices. Both valves have narrow linear axial areas and large asymmetric central areas, often reaching one or both valve margins. The raphe is straight and the short terminal fissures curve to opposite sides.

Monoraphid - Valves are linear-elliptical. The raphe valve has a bow tie-shaped central area. The raphe has long terminal raphe fissures curved to opposite sides of the valve. The rapheless valve has a large rounded, hexagonal or diamond-shaped central area. Striae are radiate on both valves, 24-30 in 10 µm.

Monoraphid - Valves are elliptic to elliptic-lanceolate. The raphe valve has linear axial area and transversely rectangular to bow-tie shaped central area, which is slightly asymmetric or symmetric. The rapheless valve has a lanceolate axial area and a large, transverse, asymmetric central area with a rimmed depression on the internal valve surface. The striae are radiate on both valves.

Monoraphid - Valves are elliptical to linear-elliptic. The raphe valve has a linear axial area and a small asymmetric central area. The rapheless valve has a rhomboid axial area, which often has an irregular border. The central area on rapheless valve is usually not differentiated from the axial area. Striae are slightly radiate in the center and strongly radiate at the apices of both valves, 25-31 in 10 µm. Areolae are often visible in LM.

Monoraphid - Valves are elliptical-lanceolate to linear-elliptical. The raphe valve has a linear axial area, which widens toward the center of the valve, and a transversely elliptical central area. The raphe is straight, without terminal fissures. The rapheless valve has a wide rhomboid-lanceolate axial area. Striae are radiate on both valves, 23-27 in 10 µm.

Monoraphid - Valves are elliptic. The raphe valve has a narrow linear axial area and transversely rectangular, or elliptic central area. The raphe is straight. The rapheless valve has a narrow linear axial area and an asymmetric central area. Areolae number 35–40 in 10 μm within each stria.

Monoraphid - Valves are linear-elliptical. The raphe valve has a linear to linear-lanceolate axial area, which widens toward the center of the valve, and a transversely elliptical to rectangular central area. The raphe is straight, without terminal fissures. The rapheless valve has a rhomoid axial area, which often sharply widens in the valve center. Striae are radiate on both valves, 27-30 in 10 µm.

Monoraphid - Valves are elliptic. Both valves have narrow linear axial areas and transversely rectangular central areas. The central area on the rapheless valve may be asymmetric. The raphe is filiform and straight. There are 25 areolae in 10 μm along the stria.

Monoraphid - Valves are very small and elliptical, with radiate striae. The raphe valve has a 'bow-tie-shaped' central area.

Symmetrical biraphid - Valves linear-elliptical to broadly rounded, ends not produced. Striae are composed of distinct puncta. A small lyre-shaped hyaline area is found on either side of the axial area.

Araphid - Valves at the larger end of the size spectrum of P. brevistriata are lanceolate with rostrate ends. Smaller specimens are elliptical with rounded ends. The axial area is broad and lanceolate. Striae restricted to the valve margin. Striae are distinct, composed of wide, round to oval areolae. Spines are positioned on the valve mantle, in line with the striae. The spines are solid and spatulate.

Araphid - PSEUDOSTAUROSIRA ELLIPTICA HAS NOT BEEN VERIFIED IN NORTH AMERICA Valves of P. elliptica are elliptical to lanceolate with cuneate to rounded ends. Striae are short and usually composed of one round areola on the valve face and another on the valve mantle.

Araphid - Valves are lanceolate to elliptic, with broadly rounded ends to linear with subrostrate, rounded ends. Striae are narrower than the costae and formed by round areolae. Areolae decrease in size from valve face edge toward axial area. Spines are hollow, spatulate and positioned on the striae. Two distinct pore fields are present at each apex.

Araphid - Frustules are lanceolate with rostrate to subcapitate ends. Axial area broadly lanceolate. The striae are short, restricted to the valve margins. Apical pore fields are present at both apicies and are well developed. Under the SEM, the pore fields can be observed to be recessed below the valve surface.

Araphid - Valves are round to slightly elliptical. The axial area is typically lanceolate, but linear in some specimens. Some specimens may possess a broader axial area, but striae are never restricted to the valve margin. Spines are solid and positioned in line with striae. This taxon is difficult to recognize under the light microscope and identification may not be positive without scanning electron microscopy.