• Category
  • Length Range
    25-53 µm
  • Width Range
    12-14.5 µm
  • Striae in 10 µm
    19-22 in 10 μm on raphe valve, 16-20 on rapheless valve
  • Synonyms
    Stauroneis obliqua W.Greg.



Valves are broadly lanceolate, with obtuse or very slightly protracted apices. On the raphe valve, the raphe is oblique to the apical plane of the valve. That is, the raphe is not aligned with the apical axis, but slightly offset. Externally, the proximal raphe ends are slightly expanded. The distal raphe ends are slightly turned to opposite sides. Internally, the proximal raphe ends are turned to opposite sides.

On the rapheless valve, the sternum is not oblique, and runs from one valve apex to another and is only slightly curved. The axial area is narrow and linear. The central area is an asymmetric, wedge-shaped fascia on both valves. The facsia nearly reaches the valve margin and is bordered by short striae. The striae are radiate and punctate, with approximately 20 areolae in 10 μm.


Psammothidium obliquum is a cold-water species occasionally found in low-conductivity lakes of Alaska and northern Eurasia (Foged 1971).

Original Description

  • Basionym
    Stauroneis obliqua
  • Author
    W.Greg. 1856
  • Length Range
    25-56 µm
  • Striae in 10µm

Original Images

Psammobliquum Orig Ill1
Psammobliquum Orig Descr

Cite This Page

Potapova, M. (2020). Psammothidium obliquum. In Diatoms of North America. Retrieved May 18, 2024, from https://diatoms.org/species/psammothidium-obliquum


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