• Category
  • Length Range
    12-26 µm
  • Width Range
    5.1-7.8 µm
  • Striae in 10 µm



Valves are linear-elliptical. The raphe valve has a linear axial area and a bow tie-shaped central area. The raphe has long terminal fissures curved to opposite sides. The central raphe ends are slightly expanded externally. The central raphe ends curve toward opposite sides internally. The rapheless valve has a narrow linear axial area and a large rounded, hexagonal or diamond-shaped central area. Striae are radiate on both valves, 24-30 in 10 µm, interrupted at the valve margin. The external openings of the areolae on the valve face are circular to slightly elongated. The areolae are often visible in LM near the central area of the rapheless valve. One row of elongated areolae is present on the mantle of both the rapheless and raphe valves; a second row is present on the valve margin at the valve apices.

Original Description

Schalen typisch elliptisch, die Raphenschalen mit deutlich punktierten Transapikalstreifen (Fig. 831 g-k).

  • Basionym
    Achnanthes austriaca var. helvetica
  • Author
    Hust. 1933

Original Images

Achnanthes austriaca var. helvetica orig illus
Achnanthes austriaca var. helvetica orig descr

Cite This Page

Potapova, M. (2010). Psammothidium helveticum. In Diatoms of North America. Retrieved June 20, 2024, from https://diatoms.org/species/psammothidium_helveticum


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