• Category
  • Length Range
    16-29 µm
  • Width Range
    11-20 µm
  • Striae in 10 µm
  • Synonyms
    Navicula hummii Hustedt 1955



Valves are elliptic, with bluntly rounded poles. The valve face is covered externally by a conopeum that is best viewed in SEM. A distinct lyre-shaped canal is present, with the center constricted at the sternum and forming two elliptical spaces. The internal spaces between canals and sternum contain single rows of areolae alongside the canals. Outside the canal, striae are uniseriate and radiate slightly around the elliptical spaces. The raphe is straight with hooked terminal fissures.


This taxon is found in the brackish water of estuaries, with the images shown here from the Grand Bay National Estuarine Research Reserve, Mississippi.

Original Description

Valves broadly elliptical, 12-30 µ long, 9-20 µ broad. Raphe straight, with terminal nodules distant from the ends and long terminal fissures, central pores more or less distant. Axial area rather large, strongly contracted in the middle and forming two elliptical spaces; central area rectangular, in larger specimens a narrow hyaline band reaching the margin. Lateral areas linear, also strongly contracted in the middle and convergent at the ends, connected with the central area, separated from the axial area by a single row of puncta. Transapical striae 12-16 in 10 µ. radiate, in the middle divergent, not reaching the margin, coarsely punctate, puncta 16-20 in 10 µ.

  • Basionym
    Navicula hummii
  • Author
    Hustedt 1955
  • Length Range
    12-30 µm
  • Width
    9-20 µm
  • Striae in 10µm

Original Images

Navicula Hummii Orig Illus
Navicula Hummii Orig Desc

Cite This Page

Atchia, I., Smith, K. (2020). Fallacia hummii. In Diatoms of North America. Retrieved May 20, 2024, from https://diatoms.org/species/fallacia-hummii


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