Valves are linear and biconstricted, with apices rounded. Axial area narrow, broadening to a transverse fascia with lunate thickenings on either side of the central area. The raphe is lateral and arched slightly. The striae are radiate to parallel. A fine longitudinal line is present.

The concept for this species embraced by Krammer and Lange-Bertalot (1986) is quite broad, encompassing what appear to be many taxa. The type specimens of Ehrenberg have yet to be assessed, and this may be crucial to our understanding of the species.


Original Description

N. Silicula, testula linearis elongata , a dorso aequaliter trinodis, nodo uno medio, duobus apicalibus, hinc apicibus obtusissimis.

  • Basionym
    Navicula silicula
  • Author
    Ehrenb. 1843

Original Images

Navicula silicula orig illus

EMAP Assessment

EMAP Distribution

Caloneis Silicula 40 Copy
Map 40

Response Plots

Caloneis Silicula Copy

Cite This Page

Kociolek, P. (2011). Caloneis silicula. In Diatoms of North America. Retrieved July 20, 2018, from


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