• Category
  • Length Range
    8.8-16.2 µm
  • Width Range
    4-5.2 µm
  • Striae in 10 µm
  • Synonyms
    Fallacia monoculata (Hust.) D.G.Mann 1990



Valves are elliptic to lanceolate, with broadly rounded ends. The central area is small and circular. The raphe is curved slightly, within a narrow axial area. Striae are radiate. A longitudinal hyaline area is present on each side of the axial area. A conopeum is present along the axial margin, and is expanded and slightly asymmetric at the center of the valve.


Recent USGS stream surveys have collected Pseudofallacia monoculata in several localities across the United States, from Georgia, North Carolina and Virginia in the east to the Willamette Valley, OR in the west. This taxon has also been observed in central Mexico (Mora et al. 2015). It is widely distributed but found in low abundance where collected.

Original Description

  • Basionym
    Navicula monoculata
  • Author
    Hust. 1945
  • Length Range
    14 µm
  • Width
    5 µm
  • Striae in 10µm

Original Images

Navicula monoculata orig illus
P Monoculata  Holo Hinz
F Monoculata Orig Desc Text

Cite This Page

Bishop, I. (2016). Pseudofallacia monoculata. In Diatoms of North America. Retrieved August 18, 2018, from https://diatoms.org/species/fallacia_monoculata


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