• Category
  • Length Range
    9.7-11 µm
  • Width Range
    4.8-5.7 µm
  • Striae in 10 µm
  • Synonyms
    Achnanthes rossii Hust.



Valves are elliptic to elliptic-lanceolate with slightly protracted apices that are most pronounced in large individuals. The valve is bent, placing the central area and the apices in separate planes of focus. The axial area is narrow and linear. On the raphe valve, the central area is narrow, irregular, and transversely rectangular, bordered by 3-4 shortened striae. On the rapheless valve, the central area is moderately wide, rhombic to lanceolate. The striae are slightly radiate throughout and slightly curved in opposite directions at the apices. The areolae are visible in LM, particularly on the raphe valve.


Psammothidium rossii prefers low nutrient, low conductivity, but not not acidific waters (Cantonati et al. 2017). This species is considered to be widespread in distribution, but it is typically low in abundance.

Original Description

99. A. Rossii nov. spec. Valvae elliptico-lanceolatae apicibus obtuse rostratis, 10-15 μ lonage, 5-6 μ latae. Rhaphovalva rhaphai dis-recta fissuris terminalibus in diversas partes carvatis, area axiali angustissima, area centrali Paulo transapicaliter in fasciam an-gustam brevemque dilatate, striis transapicalibus leniter radiant-bus, circiter 33 in 10 μ. Areovalva area axiali angusta, area cent-rali parva, transapicaliter dilatate, striis transapicalibus leniter radiantibus, circiter 33 in 10 μ. Fig. 12-20.

Schalen elliptisch-lanzettlich mit stumpf geschnäbelten Enden, 10-15 μ lang, 5-6 μ breit. Raphenschale mit gerader Rhaphe mit nach entgegengestzten Seiten abgebogenen Polspalten, Axial-area sehr eng, Zentralarea etwas transapical zu einer schmalen und kurzen Querbinde erweitert, Transapikalstreifen leicht radial, um 33 in 10 μ. Rhaphenlose Schale mit enger Axialarea, die in der Mitte etwas zu einer kleinen Zentralarea erwetert ist, die ent-weder rundlich oder ebenfalls als kurze Querbinde entwickelt ist, Transapikalstreifen wie auf der Rhaphenschale etwa 33 in 10 μ und ebenfalls leicht radial.

Nicht selten im Weinfelder und Geündener Maar. Die Art ist verwandt mit A. lapponica HUST., von der sie sich besonders durch die abweichende Entwicklung der Areas unterscheidet. Ich widme sie meinem Korrespondenten, Herrn R. Ross, British Museum (Natural History) in London.

  • Basionym
    Achnanthes rossii
  • Author
    Hust. 1954
  • Length Range
    10-15 µm
  • Width
    5-6 µm
  • Striae in 10µm

Original Images

Psammothidium Rossii Orig Illus
Psammothidium Rossii Orig Desc

Cite This Page

Tyree, M. (2018). Psammothidium rossii. In Diatoms of North America. Retrieved September 28, 2020, from https://diatoms.org/species/psammothidium-rossii


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