• Category
  • Length Range
    30-35 µm
  • Width Range
    10.0-12.6 µm
  • Striae in 10 µm
    18 (center) -26 (ends)



Valves are elliptic with bluntly rounded, subtly protracted apices. The axial area is very narrow. The central area is circular and about half the width of the valve. Proximal raphe ends are dilated, straight and extend into the central area. Striae are radiate; they are shorter and more widely spaced about the central area. Areolae are very fine and number about 40 in 10 µm.


There are 23 records of Sellaphora bacilloides in the Montana Diatom Collection, from lakes and low-gradient streams in arid regions throughout the Northwest United States. This uncommon species prefers alkaline waters (mean pH = 7.8) with somewhat elevated electrolytes (mean specific conductance = 689 µS/cm).

Little  Dry  Creek 2 1
Credit: Loren Bahls
Little Dry Creek at Flowing Well, Garfield County, Montana: home of Sellaphora bacilloides.

Original Description

  • Basionym
    Navicula bacilloides
  • Author
    Hust. 1945
  • Length Range
    20-30 µm
  • Width
    10-11 µm
  • Striae in 10µm

Original Images

N Bacilloides Orig Illus
Sellabacilloides Origimages
N Bacilloides Orig Des

Cite This Page

Bahls, L. (2012). Sellaphora bacilloides. In Diatoms of North America. Retrieved June 20, 2024, from https://diatoms.org/species/sellaphora_bacilloides


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