Observations by natashaphillips

Valves clavate with rounded apices. Frustules heteropolar, appearing bent in girdle view. Ventral valve concave. Dorsal valve convex. Central area oval to elliptic. Pseudoseptum present at both poles on valve margins. Striae uniseriate. Areolae apically elongated.

Raphe canal aligned with ventral margin at distal ends, the central arch of the canal is approximately 7-8 um above the ventral margin. In 10 um there are approximately 9-10 striae and 4-5 costae. Epithemia turgida contains nitrogen-fixing cyanobacteria, which enables it to live in habitats with a low Nitrogen to Phosphorus ratio.

Dorsiventral valve face with a strongly convex dorsal margin and a weakly concave ventral margin. My population is between 25-35 um long, 6-10 um wide. 12 striae and 8 costae in 10 um. The raphe canal runs along the ventral margin at the distal ends of the valve and arches towards the dorsal margin at the valve center. The apex of the canal almost reaches the dorsal margin.

The larger valves I have found in this population are undulating to form two nodes, giving this specimen the variety form binodis. Valves have rostrate to subcapitate ends. The central margin is constricted in these specimens because they are longer. The valve face is flat or slightly undulate due to coarse/raised costae. The valve face or mantle junction forms a distinctively sharp angle.

Valves are semi-lanceolate to semi-elliptical. The dorsal margin is subtly arched in the larger specimen, more dramatically arched in the smaller specimen.

Sample was taken with a 20 um net, planktonic sample.

Valves are broadly linear with a central pinch and taper into blunt ends. Striations between ribs are defined by fine striae. Raphe is contained in a canal around the margin of the valve. Undulations are oriented across the face and persist throughout the entire length of the valve face.

Valves are concentrically undulate discs with a convex, or concave, valve face. The valves are large and robust. Areolae large and circular to trapezoidal to sub-hexagonal in shape, arranged in uniseriate rows in the valve center, and become fasciculate in the outer 2/3 of the valve radius.

Valves are asymmetric, with broad headpole, almost as wide as the central area. Footpole is narrow and rounded, with pore field bisected by the distal raphe. Axial area is wide and linear-lanceolate. Raphe is complex and lateral. Central area is small, central striae of variable length. Central area contains a single isolated stigma. Striae are parallel to slightly radiate.

Valves are small, disc-shaped, with a concentrically undulate valve face. Valve faces are complementary, with scutate (raised) and lacunate (depressed) valves. Areolae are dispersed randomly at the valve center and arranged in multiseriate fascicles toward the margin.

Valves heteropolar. Headpole broadly rounded, footpole cuneately rounded to broadly rounded. Valves slightly undulate. Costae extend from margin to apical axis. Length range found in this sample 25.60-37.2 um.

Valves dorsi-ventral, with relatively even area on dorsal and ventral sides. Rounded apices. Outline of valve cymbelliform-lanceolate. Central portion of ventral margin is slightly convex. Central area circular to oval. A single stigma is present between proximal raphe ends. Length range in this sample from 105.21-127.70 um.

Valves linear, with apices bent towards the ventral margin. The center is deflected slightly towards the dorsal margin and notched. The raphe is positioned in a canal. Costae are prominent, and extend across the valve face.

Melosira varians is very common in rivers and lakes across North America. This species is considered to be tolerant of poor water quality. M. varians is primarily found in benthic habitats, with cells joined in long filamentous chains.

B. paxillifer has a long, narrow and linear valve, with a centrally located keel containing the raphe. Striae are distinct, course and parallel and perpendicular to the keel. Living cells are joined in colonies, which are joined by hooks along the keel.

Valves disc-shaped, with narrow mantle. Valve face may be flat or transversely undulate. Central area is distinct and isolated from the marginal chambered striae. Central area covers 1⁄ 2 to 1⁄ 3 of the valve face and contains 1-4 fultoportulae. The number of costae in 10 µm is 12-15. Length of diameter in this sample ranged from 10.35-16.9 um.