• Category
  • Length Range
    4.9-8.5 µm
  • Width Range
    3.5-4.0 µm
  • Striae in 10 µm
  • Synonyms
    Psammothidium curtissimum (J.R.Carter) Aboal in Aboal, Alvarez-Cobelas, Cambra and Ector



Valves are elliptic to linear-elliptic. The raphe valve has a linear axial area and a small transversely elongated central area formed by one to three shortened striae on each side. External openings of the areolae are large, square or rectangular, occasionally elongated.The raphe is straight, without terminal fissures. The central and terminal raphe ends are slightly expanded externally. Internally, the proximal raphe ends curve toward opposite sides.

The rapheless valve has a linear-lanceolate or narrowly rhomboid axial area, and a small transversely elongated central area.

Striae are radiate on both valves, 27-31 in 10 µm. Striae are interrupted at the valve margin. One row of areolae is present on the mantle. External openings of the areolae are usually small and circular to silt-like. Internal openings of the areolae on the faces of both valves are square, on the mantle they are elliptic.


Original Description

  • Basionym
    Cocconeis microscopica
  • Author
    Cholnoky 1959
  • Length Range
    7-9 µm
  • Width
    4 µm
  • Striae in 10µm

Original Images

Cocconeis Microscop Orig Ill A
Cocconeis Microscop Orig Descr


Jul 13, 2020 - Change of name

From 2010 until July 2020, this taxon appeared under the name Psammothidium curtissimum. Blanco (2016) noted that Cocconeis microscopica Cholnoky, which is a taxonomic synonym of P. curtissumum, has priority and made a new combination P. microscopicum, which is the correct name of this species . - M. Potapova

Cite This Page

Potapova, M. (2010). Psammothidium microscopicum. In Diatoms of North America. Retrieved May 24, 2024, from https://diatoms.org/species/psammothidium_microscopicum


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