• Category
  • Length Range
    22-41 µm
  • Width Range
    5.6-7.6 µm
  • Striae in 10 µm
    12-16 at the valve center, 18-20 near the ends
  • Reported As
    Cymbella aequalis (Krammer and Lange-Bertalot 1986, p. 325, pl. 134, figs. 1-3)



Valves are weakly dorsiventral and lanceolate with subrostrate apices deflected slightly to the ventral side. Valve shoulders are lacking. The axial area is narrow. The central area is small, formed by the two opposing shorter and more widely spaced central striae. The raphe is lateral with weakly inflated proximal ends that are deflected toward the dorsal margin. Distal raphe ends are hooked toward the ventral margin. Striae are weakly radiate except at the valve center and near the apices, where they are parallel. Areolae are very fine and difficult to resolve in LM.


This taxon is widely distributed and locally abundant in lakes throughout the Northern Rockies and North Cascade Mountains (Bahls 2013). These lakes are slightly alkaline (pH 7.0-7.5) with low specific conductance (10-60 µS/cm).

Summit  Lake  General 1
Credit: Barb Johnston, Parks Canada.
Summit Lake, Waterton Lakes National Park, Alberta: home of K. aequalis.

Original Description

Cymbella aequalis, W. Sm. Pl. IX. fig. 4. Length 0014"

A very distinct new species, so nearly symmetrical as to be liable at a hasty glance to be taken for a Navicula. There is however a curve at the shortly produced, obtuse extremities. The striae are fine, but not very close. This form was abundant in one gathering only, composed of coarse black peaty mud extremely difficult to clean.

  • Basionym
    Cymbella aequalis
  • Author
    W.Sm. in Grev. 1855

Original Images

Cymbella aequalis orig desc
Cymbella aequalis orig descr


May 20, 2024 - Transfer from Encyonopsis to Kurtkrammeri

This taxon page appeared under the name Encyonopsis aequalis. The genus was updated to follow the transfer to Kurtkrammeri aequalis made by Bahls (2015). - S. Spaulding

Cite This Page

Bahls, L. (2013). Kurtkrammeria aequalis. In Diatoms of North America. Retrieved May 20, 2024, from https://diatoms.org/species/kurtkrammeria_aequalis1


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