SPECIES starting with "r"

 

Asymmetrical biraphid -


Reimeria sinuata

  1. Valves linear-lanceolate with subcapitate ends
  2. Striae biseriate
  3. Isolated stigma on dorsal side of central area
  4. Ventral side of central valve expanded

Asymmetrical biraphid - Valves are linear-lanceolate with subcapitate ends. The ventral side of the central part of the valve is expanded. A stigma is present on the dorsal side of the central area. Striae are comprised of two rows of areolae (biseriate).


Reimeria uniseriata

  1. Valves linear-lanceolate with subcapitate ends
  2. Striae uniseriate
  3. Isolated stigma in central nodule
  4. Ventral side of central valve expanded

Asymmetrical biraphid - Valves are linear-lanceolate with subcapitate ends. The ventral side of the central valve is expanded. A stigma is present on central nodule. Striae are comprised of one row of areolae (uniseriate).


Rexlowea navicularis

Placoneis navicularis

  1. Apices protracted to broadly rounded
  2. Proximal raphe ends large, rounded
  3. Central area with isolated puncta
  4. Raphe lateral
  5. Raphe undulate

Symmetrical biraphid - Valves are broadly lanceolate with apices protracted to broadly rounded. The raphe is lateral and undulate. Within a stria, the marginal areolae are large and more coarsely arranged. The middle valve has areolae comparatively smaller and rounded. Central area has large, round isolated puncta. The smallest striae at the apices are multiseriate throughout their length.


Rhoicosphenia abbreviata

Gomphonema abbreviatum
Rhoicosphenia curvata

  1. Valves club-shaped
  2. Pseudoseptae present
  3. Raphe valve with full raphe system
  4. Rudimentary raphe valve with short raphe slits
  5. Central area oval

Asymmetrical biraphid - Valves are clavate, or club-shaped with rounded ends. In girdle view, frustules are distinctly arched. In valve view, the arch prevents resolution of the entire valve face at one level of focus. Pseudoseptum present at each pole. One valve possesses a fully developed raphe system, the other valve possesses short raphe slits.


Rhoicosphenia californica

  1. Apices protracted
  2. Valves narrow
  3. Axial area narrow
  4. Central area oval

Asymmetrical biraphid - Valves are linear-lanceolate and heterovalvar. The valves are narrow, 3-6 µm wide.The axial area is narrow on both the raphe and reduced raphe valves. The central area is small and ovate. Proximal raphe ends are relatively close together on the raphe valve. The apices are protracted, especially in larger specimens. The striae are lineate, rather than distinctly punctate.


Rhoicosphenia stoermeri

  1. Apices acute
  2. Proximal raphe ends broadly spaced
  3. Central area panduriform

Asymmetrical biraphid - Valves are linear to narrowly clavate, with acute apices. The proximal raphe ends are broadly spaced from one another and positioned within a panduriform central area. Valves range from 80 to 25 µm in length and 6-9 µm in width. Areolae are distinctly lineate and number 11–13 in 10 μm.


Rhopalodia gibba

  1. Valves linear
  2. Valves large

Epithemioid - 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.


Rhopalodia gibberula

Epithemia gibberula

  1. Valves lunate
  2. Striae 2-6 between costae
  3. Apices slightly bent ventrally ,or protracted and acutely rounded

Epithemioid - Valves are lunate, with strongly convex dorsal margins that are often slightly notched in the middle.The ventral margin is slightly concave to straight. In girdle view, frustules are broadly lanceolate to elliptical. Apices are slightly bent ventrally, or protracted and acutely rounded. The raphe is located on dorsal margin and is difficult to distinguish. Transapical costae may be slightly radiate.


Rhopalodia musculus

Cystopleura musculus
Rhopalodia gibberula var. musculus

  1. Ventral margin concave
  2. Length 12-60 µm
  3. Striae multiseriate
  4. Costae 3-5 in 10 µm

Epithemioid - Valves semi-elliptical, strongly convex along the dorsal margin, concave along the ventral margin, tapering to narrowly rounded ends. Costae distinct, numbering 3-5 in 10 µm. Striae are in rows of 2-4 between the costae.


Rossithidium anastasiae

  1. Valve linear to linear-elliptic
  2. Raphe straight
  3. Striae unseriate
  4. Raphe valve with a small or indisctinct central area
  5. Rapheless valve with a narrow linear axial area

Monoraphid - Valves are linear or linear-elliptic with rounded ends. The raphe valve has a linear axial area that gradually widens into a small or almost indistinct central area. The rapheless valve has a narrow, linear axial area and no distinct central area. Striae are uniseriate and slightly radiate.


Rossithidium nodosum

  1. Striae slightly radiate
  2. Striae biseriate
  3. Small central area
  4. Linear-elliptical shape

Monoraphid - Valves are linear-elliptical or elliptical with slightly drawn-out ends. The striae are slightly radiate throughout both valves and biseriate. The axial area is narrow. The central area is small, or absent. If present, it may be asymmetrical on the rapheless valve.


Rossithidium petersenii

  1. Valve linear to linear-elliptical
  2. Raphe straight
  3. Striae unseriate
  4. Raphe valve with a large rectangular or transverse elliptical central area
  5. Rapheless valve with a narrowly rhomboid axial area

Monoraphid - Valves are linear or linear-elliptical with rounded ends, 3.5-4.5 µm wide, 13-18.5 µm long. Raphe valve has a large transverse elliptical central area that almost reaches the valve margins. Terminal raphe fissures are absent. Rapheless valve has a narrowly rhomboid axial area and no distinct central area. Striae are uniseriate, slightly radiate, and number 32-36 in 10 µm.


Rossithidium pusillum

Achnanthes pusilla

  1. Valve linear to linear-elliptical
  2. Raphe straight, without distinct terminal raphe fissures
  3. Striae unseriate, slightly radiate throughout both valves
  4. One or two striae in the center of the raphe valve more broad than the other striae

Monoraphid - Valves are linear to linear-elliptical or linear-lanceolate with rounded ends. The terminal raphe fissures are not distinct. The striae are uniseriate, with 4-5 areolae per stria, and slightly radiate throughout both valves.