Encyonema norvegicum

(Grunow) A.Mayer 1947      Category: Asymmetrical biraphid
BASIONYM: Cymbella norvegica Grunow in Schmidt et al. 1875
SYNONYM(S): Encyonema norvegica (Grunow) Bukht. 1995 

Encyonema nicafei


Encyonema obscurum

LM scalebar = 10 µm = 80 pixels.


Contributor: Carrie Graeff - March 2012
Length Range: 25-43 µm
Width Range: 7.0–8.0 µm
Striae in 10 µm: Dorsal: 12–13 at the center, 14–15 at the ends; ventral: 13–15 at the center, 15–17 at the ends


Valves moderately dorsiventral with moderately rounded apices. Dorsal margin moderately arched, with most prominent dorsal arching at the lower limits of the valve size range. Ventral margin slightly tumid or slightly concave at valve center, giving the margin a slightly triundulate or biundulate appearance. Axial area narrow and central area asymmetric, with a slightly or moderately rounded central area on the dorsal side of the valve. External areolae generally dumbbell shaped, but may be bent into V- or Y-shapes, especially at the valve center. Striae slightly radiate at valve center and becoming parallel, or slightly convergent near the apices. Internally, alveoli formed by connected rectangular openings resembling a string of beads. Transapical costae are broad and not prominent. Raphe very slightly dorsally displaced with dilated external proximal raphe ends. Internally, proximal raphe ends strongly curved dorsally and raphe terminating distally in a small helictoglossae.

Original Description

Basionym: Cymbella norvegica
Author: Grunow in Schmidt et al. 1875
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Graeff, C. (2012). Encyonema norvegicum. In Diatoms of the United States. Retrieved April 20, 2018, from http://westerndiatoms.colorado.edu/taxa/species/encyonema_norvegicum

Species: Encyonema norvegicum

Contributor: Carrie Graeff

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.

Patrick, R.M. and Reimer, C.W. (1966). The Diatoms of the United States exclusive of Alaska and Hawaii, V. 1. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Schmidt, A. (-). (1874-1959). Atlas der Diatomaceen-Kunde, von Adolf Schmidt, continued by Martin Schmidt, Friedrich Fricke, Heinrich Heiden, Otto Muller, Friedrich Hustedt. Reprint 1984, Koeltz Scientific Books, Konigstein, 480 plates.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Encyonema norvegicum CAS

NCBI Genbank Taxonomy

Encyonema norvegicum NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 110030

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

Encyonema norvegicum

EMAP Response Plots

Encyonema norvegicum

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.