• Category
  • Length Range
    27-43 µm
  • Width Range
    6.4-9.4 µm
  • Striae in 10 µm



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.


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 6  Nuphar  Pool
Credit: Loren Bahls
Bloody Dick Pond No. 6, Beaverhead County, Montana: home of Stauroneis pseudagrestis.

Original Description

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

Original Images

Stpseudagrestis Origimag
Stpseudagrestis Origdesc

Cite This Page

Bahls, L. (2012). Stauroneis pseudagrestis. In Diatoms of North America. Retrieved July 15, 2024, from https://diatoms.org/species/stauroneis_pseudagrestis


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Stauroneis pseudagrestis from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.