• Category
  • Length Range
    17-38 µm
  • Width Range
    8-13 µm
  • Striae in 10 µm
    24-28 in the center, more fine towards the apices, 32-34



Valves are elliptical with rounded apices, not protracted. The axial area is narrow and straight. The raphe is straight and filiform. A lyre-shaped unornamented area bisects the striae on either side of the axial area, connecting to form the central area. The striae are radiate and finely punctate.

Original Description

  • Basionym
    Navicula pygmaea
  • Author
    Kütz. 1849

Cite This Page

Kociolek, P. (2011). Fallacia pygmaea. In Diatoms of North America. Retrieved July 15, 2024, from https://diatoms.org/species/fallacia_pygmaea


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