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Diatoms of the United States is now known as Diatoms of North America.
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GENERA starting with "t"


Tabellaria 2

  1. Valve elongate, swollen in the middle, capitate
  2. Rimoportula present at midvalve
  3. Frustules with numerous copulae
  4. Cells form zig-zag colonies

Araphid - Tabellaria valves are elongate with capitate ends. The valves are generally wider at the center than at the ends. A rimoportula is present in the center of the valve face. Septa are present on the numerous copulae (girdle bands). Pseudosepta may also be present. Cells form zig-zag colonies joined by mucilage pads secreted from apical porefields. Tabellaria is considered a close relative of Oxyneis. The two genera share...

Tabularia 1

  1. Valves with broad sternum
  2. Striae broad, shortened
  3. Apical porefield at each pole
  4. Rimoportula single on each valve

Araphid - The species in Tabularia are robust and “needle-like”, with a broad sternum. The striae are relatively broad and composed of complex areolae. An apical porefield is present at each pole. Each valve possesses a single rimoportula, positioned near one pole. Tabularia includes species that were formerly considered in Synedra, including S. tabulata and S. fasciculata. Members of the genus are found in marine and brackish...

Terpsinoƫ 1

  1. Valves elongate, margins undulate
  2. Valve center with rimoportula
  3. Porefields present at valve apices
  4. Transverse costae distinct

Centric - TerpsinoĆ« is a multipolar, ‘centric’ diatom. The frustules are heavily silicified and elongate, with strongly undulate margins. Porefields are located at the valve apices. Internal, heavily silicified transverse costae are present. In girdle view, the transverse costae appear to form the shape of musical notes. Rimoportulae are positioned near the center of the valve face. TerpsinoĆ« grows commonly in tropical and...

Tetracyclus 3

  1. Striae pattern scattered or less regular at sternum
  2. Valve mantle with prominent hyaline step
  3. Copulae with multiple ornamented pattern

Araphid - Frustules of Tetracyclus are heavily silicified. Valves are isopolar, with a flat surface. The valve mantle is relatively deep and possesses a prominent hyaline step. The valve face may be elliptical to elongate (some taxa are even circular) and the apicies are often capitate. Primary internal transapical ribs are present, and some species may possess secondary and tertiary transapical ribs. The valve margin may be...

Thalassiosira 3

  1. Valve face flat or tangentially undulate
  2. Fultoportulae one to several near the center valve
  3. Valve margin with spines or occluded processes
  4. Mantle narrow

Centric - The valve face of most freshwater species of Thalassiosira is flat, although some are tangentially undulate. The mantle is usually relatively narrow. Striae are radial and not arranged in fascicles. Marginal fultoportulae are positioned near marginal spines, or occluded processes. One to several fultoportulae are also located near the center of the valve face, often in a circular array. Species of Thalassiosira grow...


  1. Valves elongate with capitate apices
  2. Valves heteropolar
  3. Rimoportulae 2-5

Araphid - SPECIES OF TIBETIELLA ARE NOT KNOWN TO OCCUR IN NORTH AMERICA Cells are linear-elongate with capitate apices. Valves are heteropolar in valve view and nearly rectangular or trapezoidal in girdle view. Striae are uniseriate and parallel, but may be radiate near the apices. The sternum is narrow, expanding to a rectangular central area. Two to five rimoportulae are present at each apex, positioned adjacent to the sternum....

Tryblionella 4

  1. Raphe eccentric
  2. Valve face with longitudinal undulation

Nitzschioid - Valves are typically linear-lanceolate to elliptical in some species. Like Nitzschia, Tryblionella possesses an eccentric raphe, positioned in a canal along one valve margin. The raphe systems within a frustule are positioned on opposite, in the manner of nitzschioid symmetry. The raphe canal is supported by fibulae. Valves have a distinct longitudinal undulation on the face. Although Tryblionella was described in 1853,...