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Encyonopsis microcephala

(Grunow) Krammer 1997      Category: Asymmetrical biraphid
BASIONYM: Cymbella microcephala Grunow

Encyonopsis lacuscaerulei


Encyonopsis montana

LM scalebar = 10 µm = 80 pixels.


Contributor: Pat Kociolek - March 2011
Length Range: 10-16 µm
Width Range: 3-4 µm
Striae in 10 µm: 22-24


Valves are asymmetrical to the apical axis, the dorsal margin is distinctly convex, then ventral margin is slightly convex. The apices are protracted and relatively large compared to the size of the valve, broadly rounded, and curved slightly towards the dorsal margin. The axial area is narrow. The central area is indistinct, when present it is formed by a short stria on the ventral margin. The raphe is filiform and slightly arched towards the dorsal margin. Striae are parallel on the dorsal margin, radiate on the ventral margin.

Original Description

Basionym: Cymbella microcephala
Author: Grunow
Length Range: µm
Striae in 10 µm:

Original Description

C. microcephala Grun. (Atl. Ρ1. VΙΙΙ fig. 36-39 — in Type Νο 211.) Valves assez étroitement lanceolées, à peine cymbiformes, à extrémités fortement rostrées-capitées ; raphé faiblement arqué ; stries délicates, 24 dans les grandes formes, 28 à 30 dans les petites formes. Longueur : 1 1/2 à 2 1/3 c.d.m.

Original Images

Cite This Page:
Kociolek, P. (2011). Encyonopsis microcephala. In Diatoms of the United States. Retrieved May 22, 2018, from

Species: Encyonopsis microcephala

Contributor: Pat Kociolek

Reviewer: Sarah Spaulding


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)

Encyonopsis microcephala CAS

North American Diatom Ecological Database (NADED)

NADED ID: 203002

Autecology Discussion

EMAP Assessment

The Environmental Protection Agency (EPA) western Environmental Monitoring and Assessment Program (EMAP) study was completed during the years 2000-2004 (see citations at bottom of this page). Over 1200 streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming) were selected for sampling based on a stratified randomized design. This type of design insures that ecological resources are sampled in proportion to their actual geographical presence. Stratified randomized design also allows for estimates of stream length with a known confidence in several “condition classes” (good or least-disturbed, intermediately-disturbed, and poor or most-disturbed) for biotic condition, chemistry and habitat.

EMAP Distribution

Encyonopsis microcephala

EMAP Response Plots

Encyonopsis microcephala

EMAP citations

Results are published in:

Johnson, T., Hermann, K., Spaulding, S., Beyea, B., Theel, C., Sada, R., Bollman, W., Bowman, J., Larsen, A., Vining, K., Ostermiller, J., Petersen, D. Hargett, E. and Zumberge, J. (2009). An ecological assessment of USEPA Region 8 streams and rivers. U.S. Environmental Protection Agency Region 8 Report, 178 p.

Stoddard, J. L., Peck, D. V., Olsen, A. R., Larsen, D. P., Van Sickle, J., Hawkins, C. P., Hughes, R. M., Whittier, T. R., Lomnicky, G. A., Herlihy, A. T., Kaufman, P. R., Peterson, S. A., Ringold, P. L., Paulsen, S. G., and Blair, R. (2005). Environmental Monitoring and Assessment Program (EMAP) western streams and rivers statistical summary. U.S. Environmental Protection Agency Report 620/R-05/006, 1,762 p.

Stoddard, J. L., Peck, D. V., Paulsen, S. G., Van Sickle, J., Hawkins, C. P., Herlihy, A. T., Hughes, R. M., Kaufman, P. R., Larsen, D. P., Lomnicky, G. A., Olsen, A. R., Peterson, S. A., Ringold, P. L., and Whittier, T. R. (2005). An ecological assessment of western streams and rivers. U.S. Environmental Protection Agency Report 620/R-05/005, 49 p.