SPECIES starting with "t"

Araphid - The central inflation is as wide, or slightly wider, than the capitate apices. Central striae reach the axial line, so there is no hyaline central area. Girdle bands open, with regular septae. Rudimentary septae are absent. Marginal spines are absent.

Araphid - Valves with central valve inflation and capitate, to slightly capitate ends. The central inflation is wider than the terminal inflation. A hyaline area is present in the central valve. Marginal spines are present. A rimoportula is located near the central area. Regular and rudimentary septa are present on closed girdle bands.

Araphid - Valves are linear-lanceolate to lanceolate. The apices are set off slightly, rounded but not capitate. The axial area is very broad. No central area is evident. Striae are costate.

Centric - Valves are triundulate, except in specimens at the lower end of the size spectrum. Pseudocelli are present at valve apicies.The inflations are almost equal in width. The middle inflation contains a rimoportula, positioned slightly off center. The areolae are coarse and randomly arranged. In girdle view, the silica bars resemble music notes.

Araphid - Valves are ellliptic-lanceolate with a large central inflation and rounded to pointed apices. The costae are thick and evenly spaced at 2-3 in 10 µm. The axial area is narrow and linear, sometimes with poorly defined margins. Girdle bands contain septa that extend from alternating ends in adjacent bands.

Araphid - Valves are lanceolate-elliptical, with rounded to cuneate ends. A single rimoportula is located between the first and second costa, near the sternum. Septa are present and alternate between poles in adjacent copulae. Costae number 1-3 in 10 µm. Striae number 20-27 in 10 µm.

Araphid - Valves are elliptic-lanceolate, with broadly rounded apices. Septae are distinct and extend approximately 1/4 of the way into the valve and alternate orientation from one band to the next. Costae are robust and parallel. A single rimoportula is present at one valve end.

Centric - The valve face is flat. Areolae are coarse and radiate from the valve center in sectored rows. Three rimoportulae are present on the valve face, closer to the valve margin than to the center of the valve.

Centric - The valve face is tangentially undulate. Striae are coarse and organized into somewhat radial rows. A ring of marginal fultoportulae is present. A prominent rimoportula is present on the valve face, close to the margin.

Centric - Valves are flat, with short mantles. Areolae are fine. A single, prominent rimoportula is present on the valve margin.

Nitzschioid - Valves are constricted in the middle on both sides of valve. The apices are apiculate to subcapitate. A longitudinal fold present, forming a hyaline area. Fibulae and striae are equal in number and aligned with one another.

Nitzschioid - Valves are linear and slightly concave in the middle of the valve. The apices narrow, drawn out and narrowly rounded. A narrow, indistinct fold runs along the longitudinal axis of the valve. The fold is barely undulate, or may not appear elevated or depressed from the main valve surface. Transapical ribs are distinct. Striae are indistinct.

Nitzschioid - Valves large and fusiorm.The longitudinal undulation is distinct. Both transapical costae and fibulae are relatively faint. Striae are difficult to observe with LM.

Nitzschioid - Valves linear, slightly concave in the middle, with the ends protracted slightly and bluntly rounded. Raphe keel with distinct fibulae numbering 8-11 in 10 µm. A longitudinal fold is wide, running the entire length of the valve.