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.

Stauroneis pseudagrestis

Lange-Bert. and Werum 2004      Category: Symmetrical biraphid

Stauroneis pikuni


Stauroneis reichardtii

LM scalebar = 10 µm = 80 pixels.


Contributor: Loren Bahls - May 2012
Length Range: 27-43 µm
Width Range: 6.4-9.4 µm
Striae in 10 µm: 23-26


Valves are lanceolate with capitate apices. The axial area is narrow and widens very little or not at all near the central area. The stauros is a very broad, with curved striae on the margins. The raphe is filiform with unexpanded proximal ends that are bent slightly in the same direction. Striae are strongly radiate. Areolae are difficult to resolve in LM and number about 30 in 10 µm.

Original Description

Author: Lange-Bert. and Werum 2004
Length Range: 26-35 µm
Width Range: 6.5-7.0 µm
Striae in 10 µm: 24-27

Original Description

Original Images

Cite This Page:
Bahls, L. (2012). Stauroneis pseudagrestis. In Diatoms of the United States. Retrieved May 22, 2018, from

Species: Stauroneis pseudagrestis

Contributor: Loren Bahls

Reviewer: Rex Lowe


Bahls, L. (2010). Stauroneis in the Northern Rockies: 50 species of Stauroneis sensu stricto from western Montana, northern Idaho, northeastern Washington and southwestern Alberta, including 16 species described as new. Northwest Diatoms, Volume 4. The Montana Diatom Collection, Helena, 172 pp.

Werum, M. and Lange-Bertalot, H. (2004). Diatoms in springs, from Central Europe and elsewhere under the influence of hydrogeology and anthropogenic impages. Iconographia Diatomologica 13: 1-417.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

Stauroneis pseudagrestis CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Stauroneis pseudagrestis is uncommon in the U. S. and reported to date only from three small lakes and ponds in southwestern Montana. Here it prefers slightly alkaline water (pH 7.34-7.83) with low specific conductance (31-41 µS/cm). This species was described from springs in Germany.


Bloody Dick Pond No. 6, Beaverhead County, Montana: home of Stauroneis pseudagrestis.

Credit/Source: Loren Bahls