Visit us at

Diatoms of the United States is now known as Diatoms of North America.
This site has been redesigned and updated, and will be closing soon.

Cymbopleura inaequalis

(Ehrenb.) Krammer 2003      Category: Asymmetrical biraphid
BASIONYM: Navicula inaequalis Ehrenb. 1838
SYNONYM(S): Cymbella inaequalis (Ehrenb.) Rabenh. 
REPORTED AS: Cymbella inaequalis (Patrick and Reimer 1975, p. 36, plate 5, fig. 3) 

Cymbopleura hybrida


Cymbopleura incerta

LM scalebar = 10 µm = 20 pixels.


Contributor: Steve Nelson | Loren Bahls - June 2012
Length Range: 86-190 µm
Width Range: 30-40 µm
Striae in 10 µm: 5-8 near the valve center, 8-12 near the apices


Valves are rhomboid-lanceolate and moderately dorsiventral, with strongly arched dorsal and ventral margins. Apices are bluntly rounded and subrostrate to rostrate. The axial area follows close to the valve midline. The axial area is sub-linear, narrowest near the apices and widening gradually toward the valve middle where it merges with a somewhat wider elliptical central area. The central area is about one-quarter the width of the valve. The raphe is lateral and narrows near the proximal and distal ends. Proximal raphe ends are straight and terminated in expanded pores. Distal raphe fissures are curved, concave toward the dorsal margin. Striae are coarsely punctate and radiate, becoming parallel only very near the apices. Striae tend to be curved toward the valve center. Areolae number 14-22 in 10 µm.

Original Description

Basionym: Navicula inaequalis
Author: Ehrenb. 1838
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Nelson, S., and Bahls, L. (2012). Cymbopleura inaequalis. In Diatoms of the United States. Retrieved May 22, 2018, from

Species: Cymbopleura inaequalis

Contributor: Steve Nelson | Loren Bahls

Reviewer: Sarah Spaulding


Ehrenberg, C.G. (1838). Die Infusionsthierchen als vollkommene Organismen. Ein Blick in das tiefere organische Leben de Natur. erlag von Leopold Voss, Leipzig. pp. 1-xvii, 1-548, pls. 1-64.

Krammer, K. (2003). Cymbopleura, Delicata, Navicymbula, Gomphocymbellopsis, Afrocymbella. Diatoms of Europe. Diatoms of the European Inland Waters and Comparable Habitats 4: 1-530.

Patrick, R.M. and Reimer, C.W. (1975). The Diatoms of the United States, exclusive of Alaska and Hawaii, V. 2. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA

California Academy of Sciences (CAS)

Cymbopleura inaequalis CAS
Cymbopleura inaequalis CAS

NCBI Genbank Taxonomy

Cymbopleura inaequalis NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 190014

Autecology Discussion

Cymbopleura inaequalis is widely distributed in lakes, ponds, and slow-moving streams across the United States, where it prefers somewhat alkaline waters of moderate conductivity (Patrick and Reimer 1975, Montana Diatom Database). This species has a wider ecological amplitude than most species of Cymbopleura. Because of its large size, this taxon is often overlooked during proportional counts along predetermined transects. It is probably much more widely distributed than records suggest.


Lake McDonald, Glacier National Park, Montana: home of Cymbopleura inaequalis.

Credit/Source: National Park Service Webcam Photo