GENERA starting with "e"

 

Ellerbeckia 1

  1. Valve surface flat
  2. Unique tube-like processes
  3. Frustules joined in colonies

Centric - Ellerbeckia frustules are large cylinders with relatively narrow mantles. Cells are joined into filamentous colonies, linked by an interlocking series of ridges and grooves on opposing valve faces. The valve surface is flat and lacks the pores or processes of many centric diatom genera. Two different kinds of valves comprise a colony: linking valves that connect adjacent cells within a colony, and separation valves that...


Encyonema 10

  1. Dorsal margin highly arched
  2. Ventral margin straight or nearly straight
  3. Stigmoids present or absent, if present then located on the dorsal central area
  4. Distal raphe ends ventrally deflected

Asymmetrical biraphid - Encyonema frustules are asymmetrical to the apical axis and symmetrical to the transapical axis. The dorsal margin is highly arched, while the ventral margin in straight or nearly straight. Stigmoids may be present or absent. If a stigmoid is present, it is located on the dorsal side of the central area. Distal raphe ends are ventrally deflected, while distal raphe ends of Cymbella are dorsally deflected. Apical pore...


Encyonopsis 19

  1. Frustules with slight apical asymmetry
  2. Stigmoid present (dorsal) or absent
  3. Striae uniseriate
  4. Terminal raphe fissures ventrally deflected

Asymmetrical biraphid - Valves of Encyonopsis tend to be only slightly asymmetrical in the apical axis. Some species may be nearly symmetrical to the apical axis and confused with other taxa. Striae are uniseriate. If a stigmoid is present, it will be located on the dorsal side of the central area. The raphe is positioned nearly centrally on the valve. Terminal raphe fissures are ventrally deflected. In contrast to Cymbella, the valves of...


Entomoneis 4

  1. Bilobate, raised keel
  2. Valves torsioned
  3. Raphe positioned within raised keel

Asymmetrical biraphid - The frustules of Entomoneis are structurally complex, with numerous girdle bands. Valves are lanceolate or linear with acute apices. In processed material, cells usually come to rest in girdle view, although many different viewing aspects are possible. Cells are rarely viewed in valve view (but see image with #2). The valve face is laterally compressed but highly arched to form a thin bilobate wing, or keel. The cells...


Envekadea 1

  1. Raphe sigmoid

Symmetrical biraphid - Species within the genus Envekadea are naviculoid, with a sigmoid raphe. The areolae are large and composed of rectangular to irregular polygons. Externally, the areolae are occluded by porous hymenes. The copulae are unoramented. A single chloropolast is present, which is H-shaped in valve view. Envekadea includes the former Navicula hedinii Hustedt and N. pseudocrassirostris Hustedt. Envekadea pseudocrassirostris...


Eolimna 1

  1. Cells small
  2. Sternum present, central

Symmetrical biraphid - The cells of Eolimna are small, generally less than 20 ┬Ám in length. A narrow central sternum is present, and the raphe is straight. Valves lack apical pore fields. SEM features show areolae are positioned medially within the frustule wall and are covered internally by hymens. Eolimna includes the former Navicula minima and N. adnata.


Epithemia 4

  1. Raphe eccentric, positioned along ventral margin
  2. Raphe opens internally into a canal
  3. Areolae complex

Epithemioid - Epithemia has an eccentric raphe system, positioned along the ventral margin. Each branch of the raphe is arched toward the dorsal margin. Externally, the proximal raphe slits terminate in expanded ends, while internally, the raphe slit is continuous through the central nodule. The raphe is also supported internally by large, transapical costae. The valvocopulum, which is the girdle band next to the valve mantle, often...


Eucocconeis 4

  1. Frustules with torsional twist about the apical axis
  2. Central sternum sigmoid

Monoraphid - Eucconeis frustules are bent about the median transapical plane, including a twisted, sigmoid central sternum. As a member of the monoraphid group, the frustules are heterovalvar and differ in ornamentation between the raphe valve and rapheless valve. Eucocconeis species occur commonly in the littoral zone of oligotrophic lakes, within epipelic, epipsammic, or epilithic habitats. Some species occur on wet walls.


Eunotia 35

  1. Valves with a short raphe
  2. Raphe extends from valve mantle onto valve face
  3. Striae uniserate
  4. One rimoportula usually present at valve apex

Eunotioid - Members of the Eunotiaceae (Eunotia, Actinella, Amphicampa) are unusual among the raphid diatoms in that frustules have a very short raphe system. The terminal nodules are positioned on the mantle. From the terminal nodule, the raphe slit lies on the valve mantle then slightly, or strongly, curves onto the valve face. As a result of this morphology, raphe branches visible in girdle view. Valves of Eunotia are...


Eupodiscus 1

  1. Areolae hexagonal
  2. Marginal ocelli present
  3. Marginal rimportulae present
  4. Margin with scalloped ridge

Centric - EUPODISCUS IS A MARINE TAXON Valves circular, with hexagonal, loculate areolae. The valve margin of the valve face possesses a scalloped, narrow ridge. Ocelli are present at the valve margins. The internal openings of the ocelli are depressed. Rimoportulae are present on the valve mantle, positioned between the ocelli. Eupodiscus is know from shallow, marine habitats.