Encyonopsis aequaliformis

L.L.Bahls 2013      Category: Asymmetrical biraphid

REPORTED AS: Cymbella descripta (Hein 1990, p. 33, pl. 9, fig. 6) 

Encyonema yellowstonianum


Encyonopsis albertana

LM scalebar = 10 µm = 80 pixels.


Contributor: Loren Bahls - May 2013
Length Range: 25-32 µm
Width Range: 5.9-7.0 µm
Striae in 10 µm: 12-15 at the valve center, 16-19 near the apices


Valves are weakly dorsiventral, lanceolate to elliptic-lanceolate with capitate apices deflected slightly to the ventral side. Valve shoulders are lacking. In smaller valves there is slight asymmetry on either side of the transapical axis, giving valves a somewhat gomphonemoid appearance. The axial area is narrow. The central area is small, formed by the two opposing shorter and more widely spaced central striae. The raphe is lateral with weakly inflated proximal ends that are deflected toward the dorsal margin. Distal raphe ends are hooked toward the ventral margin. Striae are radiate except at the valve center and near the apices, where they are parallel. Areolae are very fine and difficult to resolve in LM.

Original Description

Author: L.L.Bahls 2013
Length Range: 25-32 µm
Width Range: 5.9-7.0 µm
Striae in 10 µm: 12-15 at the valve center, 16-19 near the apices

Original Description

Valves lanceolate to elliptic-lanceolate, not or slightly dorsiventral. Apices distinctly capitate. Valve length 25–32 μm; valve width 5.9–7.0 μm. Axial area narrow. Central area small, defined by a shortened median stria on each side. Raphe weakly lateral and nearly straight, close to the valve midline. Proximal raphe ends slightly dilated and bent toward the dorsal side. Distal raphe fissures hooked toward the ventral side. Striae moderately radiate, parallel to weakly convergent near the apices, 12–15 in 10 μm at valve center, 16–19 in 10 μm near the apices.

Original Images

Cite This Page:
Bahls, L. (2013). Encyonopsis aequaliformis. In Diatoms of the United States. Retrieved April 21, 2018, from http://westerndiatoms.colorado.edu/taxa/species/encyonopsis_aequaliformis

Species: Encyonopsis aequaliformis

Contributor: Loren Bahls

Reviewer: Mark Edlund


Bahls, L. (2013). Encyonopsis from western North America: 31 species from Alberta, Idaho, Montana, Oregon, South Dakota, and Washington, including 17 species described as new. Northwest Diatoms, Volume 5. The Montana Diatom Collection, Helena, 46 pp.

Hein, M. (1990). Flora of Adak Island, Alaska: Bacillariophyceae (Diatoms). Bibliotheca Diatomologica (H. Lange-Bertalot, ed.), Band 21, J. Cramer, Berlin, 133 pp.+ 53 plates.

Krammer, K. (1997). Die cymbelloiden Diatomeen. Eine Monographie der weltweit bekannten Taxa. Teil 2. Encyonema part., Encyonopsis and Cymbellopsis. Bibliotheca Diatomologica 37:1-469.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)


Autecology Discussion

Encyonopsis aequaliformis has been collected from a pond and a small lake on Adak Island, Alaska (Hein 1990) and from three lakes in western Washington (Bahls 2013).


Nada Lake, Chelan County, Washington: type locality of Encyonopsis aequaliformis.

Credit/Source: Ryan Davis, Adventurers and Scientists for Conservation