SPECIES starting with "c"

 

Caloneis bacillum

  1. Valves linear to linear-lanceolate
  2. Fascia asymmetric

Symmetrical biraphid - Valves linear to linear-lanceolate. Axial area linear, expanded at the central valve to form a broad transverse fascia. The fascia is typically asymmetric.


Caloneis lewisii

  1. Valve margin triundulate
  2. Central area with lunate markings
  3. Centra area large, rhomboidal
  4. Apices round to cuneate

Symmetrical biraphid - The species can be easily identified by its triundulate shape. The central area is large, rhomboidal and contains two lunate markings on each side of the central nodule.


Caloneis silicula

  1. Valves biconstricted
  2. Lunate thickenings near central area
  3. Longitudinal line present

Symmetrical biraphid - Valves linear and biconstricted. The axial area is narrow, broadening to a transverse fascia with lunate thickenings on either side of the central area. A fine longitudinal line is present near the valve margins.


Campylodiscus hibernicus

Campylodiscus noricus var. hibernicus

  1. Valves saddle-shaped
  2. Canal raphe raised on a keel
  3. Radial ridges present

Surirelloid - Cells are solitary, with saddle-shaped valves. Frustules are large. The valves are curved in the apical and transapical planes. The raphe is positioned at the valve margin, within a raised keel.


Capartogramma crucicula

  1. Valves elliptical-lanceolate
  2. Apices rostrate to subcapitate
  3. Stauros "X"-shaped
  4. Pseudosepta present

Symmetrical biraphid - Valves are elliptical-lanceolate with rostrate to subcapitate apices. Pseudosepta are present at the ends. A central stauros is “X”-shaped. Striae are radiate. Areolae are small, circular and number approximately 40 in 10 μm.


Cavinula cocconeiformis

  1. Valves lanceolate to elliptical
  2. Central area oval to linear-lanceolate
  3. Striae radiate
  4. Proximal raphe fissures expanded

Symmetrical biraphid - Valves are lanceolate to elliptical with narrow to broadly rounded apices. The central area is oval to linear-lanceolate and bordered by a row of elongated, distinct areolae. The proximal raphe fissures are expanded. The striae are punctate, radiate and in the center part of the valve, several striae are do not extend from the center valve to the margin - they are interrupted.


Cavinula davisiae

  1. Valves elliptic-lanceolate
  2. Central area large, orbicular
  3. Areolae near central area slightly enlarged
  4. Proximal raphe ends expanded
  5. Distal raphe fissures deflected in opposite directions

Symmetrical biraphid - Cavinula davisiae has elliptic-lanceolate valves with broadly rounded apices. The central area is large, orbicular and areolae near the central area are enlarged. Proximal raphe ends are straight and expanded; distal raphe fissures are deflected in opposite directions.


Cavinula pseudoscutiformis

  1. Valves nearly round
  2. Central area linear
  3. Areolae round

Symmetrical biraphid - Valves are small and round. The axial area is linear, continuing through the central area. The striae are strongly radiate and composed of round areolae.


Cavinula pusio

  1. Valves elliptic
  2. Apices broadly rostrate
  3. Central area nearly linear
  4. Alternate long and short striae surround central area

Symmetrical biraphid - Cavinula pusio has elliptic valves, greater than 8 µm wide. Apices are broadly rostrate. Alternate long and short striae surround a nearly linear central area.


Cavinula scutelloides

  1. Valves elliptic
  2. Striae coarsely punctate
  3. Striae strongly radiate

Symmetrical biraphid - Valves are elliptic. The central area is small and elliptic. The external proximal raphe ends are expanded. The striae are strongly radiate and coarsely punctate. Long and short striae alternate in the central area. The stria density increases towards the apices. Areolae are elliptical and number 10-14 in 10 μm.


Cavinula scutiformis

  1. Valves elliptic
  2. Central area large, orbicular
  3. Areolae near central area enlarged
  4. Axial area widens toward central area
  5. Proximal raphe ends expanded

Symmetrical biraphid - Cavinula scutiformis has elliptic valves with a large, orbicular central area. The axial area widens gradually toward the central area. Areolae near the central area are enlarged and proximal raphe ends are expanded.


Cavinula vincentii

  1. Valves elliptic
  2. Valve face flat
  3. Areolae elliptic

Symmetrical biraphid - Valves are small and elliptic in valve outline. The valve face is relatively flat. Areolae are elliptic and may be elongated in the central part of the valve.


Chamaepinnularia mediocris

Pinnularia mediocris

  1. Valves linear to broadly oval
  2. Central valve gibbous
  3. Striae composed of single chamber

Symmetrical biraphid - Valves are linear to broadly oval, with rounded apices and a gibbous (expanded) middle. The central area is a transverse fascia: in some specimens it extends to the valve margins, in other specimens short irregular striae are present at the margins. The striae are parallel and composed of a single, elongate chamber.


Chamaepinnularia soehrensis

Pinnularia soehrensis

  1. Valves are very small
  2. Margins triundulate
  3. Striae parallel

Symmetrical biraphid - Valves are very small, less than 12 µm in length. The margins of the valves are distinctly triundulate with capitate apices. Striae are parallel and relatively broad.


Cocconeis fluviatilis

  1. Striae on both valves 12-13 in 10 µm
  2. Areolae larger near margin
  3. Raphe valve with hyaline ring

Monoraphid -


Cocconeis klamathensis

  1. Raphe valve with hyaline lines
  2. Areolae dash-like, offset

Monoraphid - Valves elliptical in outline, and strongly arched about the apical axis. The raphe valve has a narrow, linear axial area. There is a small, irregular central area. A hyaline area occurs on either side of the axial area, and forms a naviculoid shape. Striae are fine, punctate, and radiate. The rapheless valve has a narrowly lanceolate central sternum. The areolae are dash-like and offset from one another on the rapheless valve.


Cocconeis pediculus

  1. Saddle-shaped frustule
  2. Unornamented ring on raphe valve margin
  3. Rapheless valve with transapically elongated areolae

Monoraphid - The frustule is saddle-shaped because of the arched valves. Striae on the raphe valve terminate before the valve margin, creating an unornamented ring around the valve margin. Striae on the rapheless valve are transapically elongated.


Cocconeis placentula

  1. Valves relatively flat, elliptic to linear-elliptic
  2. Raphe valve with small central area
  3. Striae on raphe valve interrupted by hyaline ring
  4. Striae radiate

Monoraphid - Valves are elliptic to linear-elliptic and relatively flat. The raphe valve has a narrow axial area and a small circular or oval central area. The raphe is straight and filiform. Striae are radiate in both raphe and rapheless valves. The striae on the raphe valve are interrupted by a hyaline ring positioned close to valve margin. Areolae are usually well distinguished under LM. The valvocopula attached to the raphe valve has conspicuous fimbriae. The rapheless valve has a linear to linear-lanceolate axial area.


Cocconeis rugosa

  1. Valves broadly elliptical
  2. Striae on raphe valve interrupted by narrow, irregular hyaline lines on both sides of the axial area

Monoraphid - Valves are broadly elliptical. The entire margin of the raphe valve is bordered by a hyaline rim. The striae are interrupted at the poles by narrow, irregular lines that are located on both sides of the axial area.


Cosmioneis citriformis

  1. Valve margins broadly rounded
  2. Ends short, rostrate

Symmetrical biraphid - Valves are citriform with broadly rounded margins curving to short narrow rostrate ends. The central area is rounded and the proximal raphe ends are slightly expanded externally. Striae are punctate, radiate and curve toward the center of the valve.


Cosmioneis hawaiiensis

  1. Valve margins broadly rounded
  2. Apices capitate

Symmetrical biraphid - Cosmioneis hawai’iensis has broadly rounded valve margins and distinctly capitate apices. The proximal raphe ends are slightly expanded and the distal raphe ends are curved in the same direction. The striae are punctate, radiate and curve toward the center of the valve.


Cosmioneis reimeri

  1. Valves lanceolate
  2. Ends protracted
  3. Central area slightly expanded

Symmetrical biraphid - Valves are lanceolate with slightly rounded, protracted ends. Internally, a narrow pseudoseptum is present. The central area is slightly wider than the axial area.


Craticula acidoclinata

  1. Valves lanceolate
  2. Apices subrostrate
  3. Central area with convex sides

Symmetrical biraphid - Valves are lanceolate with subrostrate, broadly rounded apices. The central area has convex sides.


Craticula cuspidata

Navicula cuspidata
Navicula cuspidata var. heribaudii

  1. Valves with rostrate or sub-capitate ends
  2. Striae parallel, equidistant
  3. Axial area narrow
  4. Raphe filiform

Symmetrical biraphid - Valves are rhombic-lanceolate with narrow rostrate to sub-capitate ends. Striae form an orthostichous pattern with transverse, parallel striae lying equidistant and intersected by thin longitudinal costae. The axial area is narrow and widens only slightly at the central area. The raphe is filiform. The proximal raphe ends are slightly expanded and straight, or possess a slight bend. The distal raphe ends form hooks, deflected in the same direction.


Craticula halophila

Navicula halophila

  1. Valves linear-lanceolate
  2. Apices protracted, rounded
  3. Length 22-32 µm, breadth 5-7 µm
  4. Striae 15-18 in 10 µm

Symmetrical biraphid - Valves linear-lanceolate with protracted, rounded apices. Axial area narrow, straight, expanded to form a narrow, sometime narrowly elliptic central area. Striae are punctate, parallel in the middle, becoming convergent at the apices.


Craticula johnstoniae

  1. Valves lanceolate
  2. Apices rostrate to subcapitate
  3. Central area elliptic

Symmetrical biraphid - Craticula johnstoniae has lanceolate valves with rostrate to subcapitate apices. The central area is elliptic, with convex sides.


Craticula pampeana

  1. Valves lanceolate
  2. Valves very large, up to 274 µm long
  3. Apices blunt, broadly rounded

Symmetrical biraphid - Craticula pampeana has very large lanceolate valves, 139-274 µm long. The apices are blunt and broadly rounded.


Craticula sardiniana

  1. Valves lanceolate
  2. Apices not protracted
  3. Central area elliptic

Symmetrical biraphid - Craticula sardiniana has large (68-113 µm long), lanceolate valves with rounded apices. The central area is elliptic, with convex sides.


Ctenophora pulchella

Fragilaria pulchella
Synedra pulchella

  1. Valves linear, elongate
  2. Distinct fascia
  3. Rimoportula present at each pole
  4. Punctate striae

Araphid - Valves are elongate. The central area has a thickened, dome-like silicicious fascia and ghost striae may be present. Each pole has a rimoportula positioned near the axial area, positioned diagonally to the apical axis.


Cyclostephanos dubius

Stephanodiscus dubius

  1. Valve concentrically undulate
  2. Marginal costae distinct
  3. Alveolae distinct
  4. Central areolae organized or scattered

Centric - Valves are strongly concentrically undulate. Marginal costae alternate with marginal chambers, called alveolae. The central areolae of large specimens are often organized into striae, while the central areolae of smaller specimens are more irregular and scattered. Spines are absent.


Cyclotella antiqua

  1. Central star-shape
  2. Striae unequal in length
  3. Shadow lines visible

Centric - Cyclotella antiqua is a small to moderate sized centric diatom with a unique central star-shaped cluster of triangular punctate fields. Shadow lines, termed Schattenlinien in German texts, are visible among the striae. Striae are slightly unequal in length.


Cyclotella bodanica var. intermedia

  1. Stria density 11-13 in 10 µm
  2. Central area ~1/3 of total diameter
  3. Areolae in central area random to slightly-radial
  4. Rimoportulae 2-3

Centric - The central area is about 1/3 of the total diameter. In the central area, the fultoportulae and areolae are usually arranged randomly, although they may be slightly radial. Stria density is 11-13 in 10 µm. Two or three equally-spaced, or slightly unevenly-spaced, rimoportulae are located at the central ends of shortened striae.


Cyclotella gamma

  1. Striae uniseriate nearest central area
  2. Areolae closest to central area large
  3. Valves transversely undulate
  4. Two concentric rings through striae

Centric - Valves of Cyclotella gamma have a transversely undulate central area. Two concentric rings pass through the striae, one very near the valve margin and the other about two-thirds of the distance to the central area. Striae are multiseriate near the valve margin and become uniseriate near the central area, where they are composed of large individual areolae that are easily resolved in LM.


Cyclotella rossii

  1. Valve face flat
  2. Ornamentation in central area variable in size and arrangement
  3. Striae uniformly-spaced at valve margin

Centric - Valves are flat, with colliculate face and regularly-spaced, thin marginal striae. Ornamentation in the central area is variable in size and arrangement (note that areolae are absent from the central area). Striae are uniformly-spaced at the valve margin


Cymatopleura internationale

  1. Valves elliptic
  2. Apices short, apiculate
  3. Fibulae 8-9 in 10 µm

Surirelloid - Cymatopleura internationale has elliptic valves 54-72 µm long with short, apiculate apices. Fibulae number 8-9 in 10 µm.


Cymatopleura solea

  1. Valves broadly linear with a central constriction
  2. Undulations oriented across the face of the valve

Surirelloid - Valves are broadly linear with a central constriction and tapering to blunt ends. Undulations oriented across the face of the valve, occur the length of the valve.


Cymbella affinis

  1. Valves strongly dorsi-ventral
  2. Valves 6.9-9.0 μm wide
  3. Central area not distinct
  4. One stigma
  5. Areolae 25-30 in 10 μm

Asymmetrical biraphid - Valves are strongly dorsi-ventral, with subrostrate to rostrate apices. The dorsal margin is strongly arched, whereas the ventral margin is slightly convex or flat, often excised. The central area is very small or not distinct. One stigma is present at the end of the middle striae. The areolae number 25-30 in 10 μm.


Cymbella amplificata

  1. Valves moderately dorsiventral
  2. Ventral margin with tumid center
  3. Central area elliptic
  4. Stigmata 6-9

Asymmetrical biraphid - Cymbella amplificata has large moderately dorsiventral valves with a large elliptic central area and a weakly concave ventral margin with a tumid center. Stigmata number 6-9. Proximal raphe ends are straight with expanded tips.


Cymbella cosleyi

  1. Valves distinctly dorsiventral
  2. Apices rounded or subrostrate
  3. Two stigmata present
  4. Ventral margin nearly flat

Asymmetrical biraphid - Cymbella cosleyi has distinctly dorsiventral valves with subrostrate, or rounded apices. The ventral margin is nearly flat, to weakly concave and slightly gibbous in the center. Two ventral stigmata are present. Areolae number 28-30 in 10 µm and are distinguishable under LM.


Cymbella excisiformis

  1. Valves strongly dorsiventral
  2. Valves 6.1-7.1 μm wide
  3. Central area indistinct
  4. Stigma present
  5. Areolae usually distinguishable under LM

Asymmetrical biraphid - Valves are strongly dorsiventral, with subrostrate to subcapitate apices. The dorsal margin is strongly arched, whereas the ventral margin is flat or slightly gibbous. The central area is indistinct. One stigma is present at the end of a middle stria. The areolae are usually distinguishable under LM.


Cymbella janischii

Cymbella mexicana var. janischii

  1. Single stigma
  2. Elongated areolae around central area
  3. Distinct apical pore fields, not bisected by distal raphe ends

Asymmetrical biraphid - Valves with a highly arched dorsal margin. The ventral margin is straight to concave, with a tumid area in the center. The axial area is narrow and slightly enlarged at the center to form an ovoid to irregular central area. A single stigma is positioned in the center of the central area. Areolae around the central area are elongated, especially on the ventral side. The apicies possess a distinct apical pore fields and the distal raphe ends are deflected around them.


Cymbella mexicana

  1. Valves large, robust
  2. Single, large stigma present
  3. Striae 6-8 in 10 µm in central valve
  4. Areolae adjacent to axial area elongated

Asymmetrical biraphid - Valves are moderately to strongly dorsi-ventral, with rounded apices. A single, large stigma present between the proximal raphe ends, at the central nodule. The striae are coarse and strongly radiate in the center of the valve, becoming parallel near the apices. Typically, three or more striae at the center of the valve are shorter than the others. The areolae are rectangular to circular in shape, with the areolae adjacent to the raphe elongated and triangular in shape. The terminal fissures are dorsally deflected at ~90º.


Cymbella neocistula

  1. Striae distinctly punctate
  2. Central stigmata 3-5
  3. Raphe complex
  4. Areolae 16-22 in 10 µm

Asymmetrical biraphid - Striae distinctly punctate, slightly radiate. Usually 3-5 stigmata are present (occasionally 2), each located at the end of a ventral stria in the central area. The central area is small and round. The raphe is reverse lateral. Areolae number 16-22 in 10 µm.


Cymbella proxima

  1. Valves strongly dorsiventral
  2. Ventral valve margin with tumid center
  3. Central area circular
  4. Stigmata 2-5
  5. Raphe lateral, filiform at distal and proximal ends

Asymmetrical biraphid - Valves are strongly dorsiventral with acuminate rounded apices, 18-23 µm wide. The ventral margin is tumid in the middle. The central area is circular with 2-5 stigmata. The raphe is lateral near the middle of the valve, becoming filiform near the distal and proximal ends. Striae are radiate, 7-8 in 10 µm. Areolae number 14-16 in 10 µm.


Cymbella proxima f. gravida

  1. Valves with broad, rounded apices
  2. Ventral valve margin slightly concave with slightly tumid center
  3. Central area circular
  4. Stigmata 3-4
  5. Raphe lateral, filiform at distal and proximal ends

Asymmetrical biraphid - Valves are strongly dorsiventral, with broad rounded apices, 18-23 µm wide. The dorsal margin is strongly arched, whereas the ventral margin is slightly concave, but with a slightly tumid central portion. The central area is circular with 3-4 stigmata. The raphe is lateral near the middle of the valve, becoming filiform near the distal and proximal ends. Striae are radiate. Areolae number 14-16 in 10 µm.


Cymbella rainierensis

  1. Valves lanceolate, 13-16 µm wide
  2. Apices weakly protracted, apiculate or rostrate
  3. Areolae 28-34 in 10 µm
  4. Raphe lateral
  5. Central area rhomboid

Asymmetrical biraphid - Cymbella rainierensis has slightly dorsiventral valves with weakly protracted apiculate, or rostrate, apices. Valves are 13-16 µm wide the central area is rhomboid. The raphe is lateral. Areola density is 28-34 in 10 µm.


Cymbella subturgidula

  1. Valves 8-13 μm wide
  2. Valves moderately dorsiventral
  3. Two stigmata
  4. Striae 8-11 in 10 μm in valve center
  5. Areolae 17-20 in 10 μm

Asymmetrical biraphid - The dorsal valve margin is strongly arched, whereas the ventral margin is flat or slightly convex. The central area is small and elliptical. Two (rarely one or three) stigmata are present at the end of the middle striae. The areolae are apically elongated and they number 17-20 in 10 μm.


Cymbella tropica

  1. Valves 8.5-12 μm wide
  2. Valves moderately dorsiventral
  3. Stigma single, elongated
  4. Striae 9-11 in 10 μm in valve center
  5. Areolae 22-25 in 10 μm

Asymmetrical biraphid - The dorsal valve margin is strongly arched, whereas the ventral margin is slightly convex. The central area is small and elliptical. A single large, elongated stigma is present at the end of the middle stria, larger valves sometimes have two stigmata. The areolae number 22-25 in 10 μm.


Cymbella turgidula

  1. Valves 9.5-14.0 μm wide
  2. Valves slightly dorsiventral
  3. Stigmata 2 (sometimes 3)
  4. Central striae 9-11 in 10 μm
  5. Areolae 22-24 in 10 μm

Asymmetrical biraphid - The dorsal valve margin is strongly arched and the ventral margin is moderately convex. Stigmata usually 2, but may be 3; stigmata located at the end of the middle striae. The areolae number 22-24 in 10 μm.


Cymbellonitzschia diluviana

  1. Valves half-lanceolate
  2. Raphe positioned along the straight margin

Nitzschioid - Valves half-lanceolate or half-elliptical, with the keel of the raphe positioned along the straight margin, rather than along the curved margin.


Cymbopleura amphicephala

  1. Valves elliptic, weakly dorsiventral
  2. Central area very small or lacking
  3. Areolae very fine
  4. Raphe filiform

Asymmetrical biraphid - Cymbopleura amphicephala has elliptic and weakly dorsiventral valves. The central area is very small or lacking. Areolae are very fine, numbering 32-35 in 10 µm. The raphe is filiform.


Cymbopleura anglica

  1. Valves elliptic
  2. Central area large
  3. Areolae 24-28 in 10 µm
  4. Raphe lateral
  5. Apices bluntly rounded

Asymmetrical biraphid - Cymbopleura anglica has moderately large elliptic and somewhat dorsiventral valves with bluntly rounded apices and a large central area. The raphe is lateral, becoming filiform near the proximal and distal ends. Areolae in the striae are easily resolved in LM and number 24-28 in 10 µm.


Cymbopleura angustata

Cymbella angustata

  1. Valves lanceolate, subtly triundulate, very slightly dorsiventral
  2. Proximal raphe ends close, deflected ventrally
  3. Distal raphe fissures comma-shaped, deflected dorsally

Asymmetrical biraphid - Cymbopleura angustata has lanceolate valves that are subtly triundulate and very slightly dorsiventral. Proximal raphe ends are close and deflected ventrally. Distal raphe fissures are comma-shaped and deflected dorsally.


Cymbopleura apiculata

  1. Valves >50 µm in length
  2. Apices apiculate
  3. Proximal raphe ends shaped like crochet hooks

Asymmetrical biraphid - Cymbopleura apiculata has broadly elliptic valves that are greater than 50 µm long. The valve length-to-width ratio ranges from 2.9-3.3. The apices are pointed, also termed apiculate, and the proximal raphe ends are shaped like crochet hooks, or crosiers.


Cymbopleura austriaca

  1. Valves linear-lanceolate to elliptic-lanceolate, up to 107 µm long
  2. Apices obtusely rounded
  3. Axial area broad
  4. Raphe strongly reverse lateral near proximal ends

Asymmetrical biraphid - Cymbopleura austriaca has large linear-lanceolate to elliptic lanceolate valves with obtusely rounded apices, a broad axial area, and strongly reverse-lateral proximal raphe ends.


Cymbopleura crassipunctata

  1. Valves large, broadly lanceolate
  2. Axial and central area with faint spots
  3. Raphe reverse-lateral
  4. Proximal raphe ends bulbous
  5. Areolae very coarse, 10-14 in 10 µm

Asymmetrical biraphid - Cymbopleura crassipunctata has large, broadly lanceolate valves with subrostrate apices. The axial and central areas have faint spots arranged in an irregular fashion. Proximal raphe ends are reverse lateral and the central pores are bulbous. Areolae in the striae are very coarse and number 10-14 in 10 µm.


Cymbopleura edlundii

  1. Valves lanceolate
  2. Apices subrostrate, rounded
  3. Axial area wide
  4. Raphe distinctly lateral
  5. Stria density higher near apices

Asymmetrical biraphid - Cymbopleura edlundii has lanceolate valves with rounded, subrostrate apices. The axial and central areas are very wide, 1/2 to 1/3 the width of the valve. The raphe is distinctly lateral, becoming weakly reverse-lateral at the proximal and distal ends. Striae number 9-13 in 10 µm at the center and 14-16 in 10 µm near the apices.


Cymbopleura heinii

  1. Valves large, broadly elliptic-lanceolate
  2. Areolae coarse
  3. Proximal raphe ends indistinctly hooked
  4. Raphe reverse-lateral

Asymmetrical biraphid - Cymbopleura heinii has large broadly elliptic-lanceolate valves with rostrate apices. Areolae are coarse and number 16-18 in 10 µm. Proximal raphe ends are reverse lateral, with small ventrally deflected hooks. The hooks may or may not be evident depending on angle of view and depth of focus. Faint, surface spots are sometimes present in the axial and central areas.


Cymbopleura hybrida

  1. Valves linear-elliptic and slightly dorsiventral
  2. Proximal raphe ends deflected ventrally
  3. Distal raphe fissures deflected dorsally
  4. Apices rostrate to capitate

Asymmetrical biraphid - Valves are linear-elliptic and slightly dorsiventral with nearly straight margins. Valve ends are abruptly constricted to form rostrate to subcapitate apices. Proximal raphe ends have ventrally deflected hooks. Distal raphe fissures are deflected dorsally.


Cymbopleura inaequalis

Cymbella inaequalis

  1. Valves broadly rhomboid-lanceolate, strongly arched
  2. Valves large
  3. Proximal raphe ends straight, pores expanded
  4. Striae coarsely punctate

Asymmetrical biraphid - Valves are broadly rhomboid-lanceolate, with strongly arched dorsal and ventral margins. Valves are large and greater than 30 µm wide. Proximal raphe ends are straight, terminating with expanded pores. Striae are coarsely punctate, with areolae numbering 14-22 in 10 µm.


Cymbopleura incerta

Cymbella incerta

  1. Valves lanceolate, moderately dorsiventral
  2. Apices rounded
  3. Axial area narrow

Asymmetrical biraphid - Cymbopleura incerta has lanceolate, moderately dorsiventral valves with rounded apices. The axial area is narrow.


Cymbopleura incertiformis

  1. Valves lanceolate
  2. Valves barely dorsiventral
  3. Apices weakly protracted
  4. Axial area narrow

Asymmetrical biraphid - Cymbopleura incertiformis has lanceolate valves that are nearly symmetric, or just barely dorsiventral. Apices are either not protracted, or only weakly protracted. The axial area is narrow.


Cymbopleura incertiformis var. laterostrata

  1. Valves linear-lanceolate
  2. Valves barely dorsiventral
  3. Apices subrostrate to broadly cuneate
  4. Axial area narrow

Asymmetrical biraphid - Cymbopleura incertiformis var. laterostrata has linear-lanceolate valves that are nearly symmetric, that is, barely dorsiventral. The apices are subrostrate to broadly cuneate. The axial area is narrow.


Cymbopleura lapponica

  1. Valves rhombic-lanceolate
  2. Proximal raphe ends deflected ventrally
  3. Terminal fissures curved dorsally
  4. Central area relatively large

Asymmetrical biraphid - Cymbopleura lapponica has rhombic-lanceolate valves 7-10 µm wide. The central area is relatively large. Proximal raphe ends are deflected ventrally. The terminal fissures are curved to the dorsal side.


Cymbopleura lata

  1. Valves lanceolate to elliptic-lanceolate
  2. Areolae fine
  3. Proximal raphe ends straight

Asymmetrical biraphid - Cymbopleura lata has medium-sized lanceolate to broadly elliptic-lanceolate valves that are less than 100 µm in length. Areolae are fine and number 28-32 in 10 µm. Proximal raphe ends are straight, with expanded ends.


Cymbopleura metzeltinii

  1. Valves rhomboid-lanceolate
  2. Axial area moderately wide
  3. Apices not protracted

Asymmetrical biraphid - Cymbopleura metzeltinii has rhomboid-lanceolate and nearly symmetric valves with unprotracted apices. The axial area is moderately wide and nearly follows the valve midline.


Cymbopleura naviculiformis

  1. Valves elliptic-lanceolate, moderately dorsiventral
  2. Central area large and rounded
  3. Areolae very fine
  4. Raphe lateral

Asymmetrical biraphid - Cymbopleura naviculiformis has moderately dorsiventral, elliptic-lanceolate valves with a large rounded central area. The raphe is lateral and the areolae are very fine, about 35 in 10 µm.


Cymbopleura oblongata

  1. Valves nearly linear

Asymmetrical biraphid - Cymbopleura oblongata has nearly linear valves with subtly triundulate margins. Valves are not, or only slightly, dorsiventral.


Cymbopleura rupicola

  1. Valves lanceolate to rhombic-lanceolate
  2. Apices weakly protracted and narrowly rounded
  3. Striae coarsely punctate

Asymmetrical biraphid - Cymbopleura rupicola has lanceolate to rhombic-lanceolate valves with weakly protracted and narrowly rounded apices and coarsely punctate striae.


Cymbopleura subaequalis

  1. Valves lanceolate to elliptic-lanceolate, slightly dorsiventral
  2. Apices weakly protracted

Asymmetrical biraphid - Cymbopleura subaequalis has lanceolate to elliptic-lanceolate valves, with arched dorsal and ventral margins and weakly protracted apices. Valves are somewhat dorsiventral.


Cymbopleura subcuspidata

  1. Valves >50 µm long with a length/width ratio of 3.3-4.4
  2. Apices rostrate to subcapitate and bluntly rounded
  3. Proximal raphe ends shaped like crochet hooks or crosiers

Asymmetrical biraphid - Cymbopleura subcuspidata has elliptic-lanceolate valves that are more than 50 µm long and with a length-to-width ratio of 3.3-4.4. The apices are rostrate to subcapitate and bluntly rounded. Proximal raphe ends are shaped like crochet hooks.


Cymbopleura sublanceolata

  1. Valves lanceolate, slightly dorsiventral
  2. Ventral margin arched
  3. Central area large, rounded rhomboid
  4. Areolae fine
  5. Raphe lateral

Asymmetrical biraphid - Cymbopleura sublanceolata has lanceolate, slightly dorsiventral valves with arched, rather than flat, ventral margins. The central area is a large, rounded rhomboid. Areolae are very fine (~ 35 in 10 µm) and the raphe is lateral.


Cymbopleura subrostrata

  1. Valves large, broadly lanceolate
  2. Areolae coarse
  3. Proximal raphe ends hooked
  4. Raphe, near ends, filiform

Asymmetrical biraphid - Cymbopleura subrostrata has very large broadly lanceolate valves with subtly protracted apices. Areolae are coarse and number 11-15 in 10 µm. Raphe ends are filiform, rather than reverse-lateral, and proximal raphe ends are distinctly hooked towards the ventral margin.