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


Geissleria 7

  1. Annula present at poles
  2. Isolated punctum present (or absent) in the central area
  3. Valve elliptic or linear-elliptic, with rounded or rostrate ends

Symmetrical biraphid - Geissleria valves are elliptic to linear-elliptic, becoming obtuse, broadly rounded or rostrate at the ends. The striae are comprised of fine lineolate areolae; areolae are 50-80 in 10 ┬Ám. Distinctive annula are present at the poles. The annulae are comprised of one to four transapical striae that interrupt the typical striae. The raphe is straight and filiform, with straight proximal ends. Terminal raphe ends are...


  1. Valve outline linear to linear-elliptic or linear-lanceolate
  2. Valve face-mantle junction smooth
  3. Mantle deep
  4. Striae uniseriate
  5. Areolae round to elliptic

Symmetrical biraphid - Genkalia was established in 2012 to accommodate Navicula digitulus and similar taxa. Valves are linear to linear-elliptic or linear-lanceolate in outline with rounded apices. The valve face-mantle junction is smooth and the mantle is deep. External proximal raphe ends are not expanded, but are often slightly curved towards primary valve side, or they may be straight. Terminal raphe fissures are long and broadly curved to...

Gliwiczia 1

  1. Frustules monoraphid
  2. Valves elliptic
  3. Striae and areolae more dense on raphe valve than on rapheless valve
  4. Internal hood on both valves
  5. Stauros on both valves

Monoraphid - Gliwiczia was established in 2013 to accommodate Achnanthes/Planothidium calcar and similar species. This genus has monoraphid frustules with a slightly concave raphe valve and almost flat, rapheless valve. Valves are elliptic. Both valves bear an internal hood or cavum and a stauros. Striae and areolae are considerably more dense and smaller on the raphe valve as compared to the rapheless valve. The raphe is straight,...

Gomphoneis 14

  1. Valves clavate, symmetric to the apical axis
  2. Pseudoseptae present
  3. Longitudinal lines may be present
  4. Striae multiseriate

Asymmetrical biraphid - Gomphoneis valves are clavate in valve view and cuneate in girdle view. Valves are symmetric to the apical axis. Two distinct groups are currently included within the genus Gomphoneis. One group contains species (including G. herculeana and G. eriense) with multiseriate striae crossed by longitudinal lines and with stigmata. The longitudinal lines are formed by either marginal lamellae or an axial plate, both internal...

Gomphonema 41

  1. Valve outline club-shaped
  2. Single stigma present, or absent
  3. Apical pore field present
  4. Striae uniseriate

Asymmetrical biraphid - Valves are symmetric to the apical axis, and asymmetric to the transapical axis. In valve view, valves are club-shaped, or clavate. In girdle view, frustules are wedge-shaped, or cuneate. A stigma may be present on one side of the central area. An apical pore field is present and bisected by the terminal raphe. Striae are uniseriate. Striae are not crossed by longitudinal lines, as in Gomphoneis. Many species grow on...

Gomphosinica 1

  1. Valves club-shaped
  2. Striae composed of 2-3 rows of areolae
  3. Stigma present
  4. Internally, stigma covered by hood
  5. Apical pore field present

Asymmetrical biraphid - Valves are clavate, or club-shaped, in valve view. In girdle view, frustules are cuneate. Striae are composed of 2-3 rows of areolae. Internally, the proximal raphe ends are unilaterally curved. A prominent stigma is present in the central area. Externally, the stigma has a round opening. Internally, the stigma has many small, round openings. An apical pore field is present at the footpole. The pore field has with...

Gomphosphenia 2

  1. Valves cuneate
  2. Axial area broad
  3. Proximal raphe with straight ends

Asymmetrical biraphid - Valves cuneate, with straight or undulate sides. Frustules are never bent or flexed. The raphe is straight and filiform, with straight external terminal fissures (both proximal and distal). Internally, the distal raphe fissure terminates in a helictoglossa. Stigmata are absent. Striae composed of open foramina, which may be obscured externally to give the appearance of ghost striae. Apical porefields, septa and...

Gyrosigma 2

  1. Valve sigmoid
  2. Raphe sigmoid
  3. Striae in perpendicular and parallel rows

Symmetrical biraphid - Valves are sigmoid. The axial area is narrow and also sigmoid, containing a sigmoid raphe. The striae are comprised of punctate areolae and form rows that are perpendicular and parallel to the apical and transapical axes. The central area is round to elliptic. External proximal raphe ends are deflected in opposite directions from one another. In living cells, two plastids are present. Gyrosigma is characteristic of...