• Category
  • Length Range
    12-19 µm
  • Width Range
    2.7-3.8 µm
  • Striae in 10 µm
    16-20 in the valve center, 20-22 at the ends



The ventral margin is slightly concave and has subapical swellings at the proximal raphe ends. The dorsal margin is flattened with angular shoulders subtending the apices. Valves are narrow, 4.2 – 6.0 times longer than wide. The apices are capitate, dorsally recurved, and rounded. Helictoglossae are not visible in the LM. One apical rimoportula. The raphe is short and curves on to the valve face. The striae are radiate and may be faint in appearance. The areolae are unresolved in the LM.


Eunotia orthohedra is epilithic and epiphytic on bryophytes in wet walls, creeks, and waterfalls.

Original Description

Valves slightly concave with subapical swellings on the ventral margin at the proximal raphe ends, flattened on the dorsal margin with angular shoulders subtending the apices, narrow, 4.2 – 6.0 times longer than wide, 12 – 19 μm long, 2.7 – 3.8 μm wide. Apices capitate, dorsally recurved, rounded. Helictoglossae not visible in the light microscope. Rimoportula at one end. Raphe short, curved on to valve face. Striae indistinct, radiate, 16 – 20 in 10 μm at the center of the valve, 20 – 22 in 10 μm near the ends. Puncta unresolved in light microscope.

  • Author
    Furey, Lowe and Johansen 2011
  • Length Range
    12-19 µm
  • Width
    2.7-3.8 µm
  • Striae in 10µm
    16-20 in the center valve, 20-22 at the ends.

Original Images

Eunotia orthohedra orig illus 2
Eunotia Orthohedra  Textscan

Cite This Page

Furey, P. (2011). Eunotia orthohedra. In Diatoms of North America. Retrieved June 23, 2024, from https://diatoms.org/species/eunotia_orthohedra


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