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GENERA starting with "f"


Fallacia 5

  1. Valves linear-lanceolate to elliptic
  2. Hyaline area on valve face, characteristically lyre-shaped

Symmetrical biraphid - Valves of Fallacia are linear-lanceolate to elliptic, with bluntly rounded ends. A thin siliceous covering, or canopeum, covers the striae on the external valve surface. A lyre-shaped non-ornamented area is present on the valve surface. The canopeum can not be resolved in the light microscope, but slits, or linear openings of the canopeum, may be visible at the valve apices. In living cells, the canopeum may be filled...


  1. Frustules very lightly silicified
  2. Striae not visible with light microscopy
  3. Central sternum distinct

Symmetrical biraphid - The frustules of Fistulifera are very lightly silicified. Valves range in shape from linear to elliptical. Cells are small (usually < 8 ┬Ám) and possess numerous thin girdle bands, up to fourteen or more. Striae are not visible with light microscopy. The central sternum is distinct and may remain in a sample after the thin frustule has been destroyed in standard preparation. Fistulifera includes the former Navicula...

Fragilaria 9

  1. Frustules rectangular to lanceolate, in girdle view
  2. Frustules joined by spines to form colonies
  3. Single rimoportula present
  4. Girdle bands open

Araphid - Fragilaria frustules are rectangular to lanceolate in girdle view. The pattern of ornamentation on the valve face is variable, but a central sternum is generally present. Frustules are joined by small marginal spines to form ribbon like (band-shaped) colonies. A single rimoportula is present, usually positioned at a distal end. Small, apical porefields are also present. Girdle bands are open. Living cells contain...

Fragilariforma 8

  1. Central sternum very narrow, or absent
  2. Cells joined by spines to form colonies
  3. Striae uniseriate

Araphid - The valve margins of Fragilariforma are variable and may be linear, lanceolate, or elliptical with rostrate to capitate apices. In girdle view, frustules are rectangular in shape. Fragilariforma valves are characterized by a very narrow, or absent, central sternum. Striae are composed of distinct, uniseriate areolae. Frustules form linear colonies, linked by small marginal spines into ribbon like (band-shaped) colonies....

Frickea 1

  1. Distinct longitudinal ribs present
  2. Ribs extend to the helictoglossa, but do not fuse
  3. Rows of areolae present between ribs and raphe
  4. Large, T-shaped distal raphe fissures
  5. Large, T-shaped proximal raphe fissures

Symmetrical biraphid - Species within Frickea have valves that are linear-lanceolate with bluntly rounded apices. The striae are comprised of relatively small, round areolae. Internally, a set of longitudinal ribs encloses the full length of the raphe and is continuous through the center of the valve. The longitudinal ribs extend to a linear helictoglossa but do not fuse. Near the apices and central area, the areolae extend across the...

Frustulia 17

  1. Valve with distinct median longitudinal ribs
  2. Ribs form a single tip at valve ends
  3. Raphe present between longitudinal ribs
  4. Striae fine, punctate, forming transapical and longitudinal rows

Symmetrical biraphid - Frustulia valves are rhomboid to linear-lanceolate with straight to undulate margins. The striae are composed of fine areolae, arranged into patterns that appear to form both apical and transapical rows.The genus possesses distinct median, longitudinal ribs that extend most of the length of the valve. The raphe is located between the longitudinal ribs. At the valve terminus, the ribs form a single tip, or porte-crayon....