• Category
  • Length Range
    27.1-48.9 µm
  • Width Range
    8.6-12.3 µm
  • Striae in 10 µm
  • Reported As
    Eunotia tetraglyphis (Ehrenberg 1854)
    Eunotia pentaglyphis (Ehrenberg 1854)
    Eunotia polyglyphis (Grunow in Van Heurck 1881)



Valves are weaked arched with a straight to slightly concave ventral margin and a moderately arched dorsal margin. The dorsal margin has 4 to 6 bluntly pointed undulations. The apices are rostrate to subcapitate and bluntly rounded. On the dorsal side, apices are set off from the valve by a shallow notch, resulting in “nose-like” ends. On the ventral side, apices are separated from the valve by a broad, shallow notch where the raphe is positioned on the valve face. Striae are radiate throughout and composed of very fine areolae, which number 34-40 in 10 µm.

Note that valve size is related to the number of dorsal undulations. The taxa E. tetraglyphis, E. pentaglyphis and E. polyglyphis were later names (homonyms) for different sizes of E. hexaglyphis.


Eunotia hexaglyphis occurs in somewhat acid to circumneutral waters of very low conductivity. The specimens shown here are from lakes and ponds in western Montana, northern Idaho and the Sierra Nevada Mountains of California. At these sites pH ranged from 5.5 to 7.1 and specific conductance ranged from 10 to 150 µS/cm.

Original Description

  • Author
    Ehrenb. 1854

Cite This Page

Bahls, L. (2013). Eunotia hexaglyphis. In Diatoms of North America. Retrieved May 29, 2024, from https://diatoms.org/species/eunotia_hexaglyphis


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Eunotia hexaglyphis 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.