• Category
  • Length Range
    19-65 µm
  • Width Range
    12-55 µm
  • Striae in 10 µm



Valves are broadly elliptical. The raphe valve has a straight, filiform raphe that becomes slightly dilated towards the center. The entire margin of the valve is bordered by a hyaline rim. The axial area is very narrow, and broadens slightly to form a small, irregularly-shaped central area. Striae are distinctly punctate (areolae within a stria number about 19-23/10 µm) and are radiate. The striae are interrupted at the poles, and in larger specimens along a longer stretch, by narrow, irregular lines that are located on both sides of the axial area. The rapheless valve is flexed about the apical axis. The axial area is very narrow, and the central area is small or lacking. Striae are coarsely punctate.

This species is an endemic to the Pacific Northwest.


Original Description

Cocconeis rugosa sp. nov. Pl. III, Figs. 34, 35. Valvae late ellipticae, convexae, 18-63 μ longae, 12-52 μ latae ; rhaphovalva rhaphe directa filiformi, area axiali angustissima, area centrali parva irregulariter definita; striae transapicales radiantes 19-23 in 10 μ, distincte punctatae, puncta etiam 19-23 in 10 μ, praecipue ad polos versus area hyalina longitudinali interruptae ; areovalva area axialis angustissima, area centrali minima, striae transapicales radiantes, 19-20 in 10 μ, distincte punctatae, series punctorum longitudinales paulo remotiores quam striae transapicales, irregulariter undulatae.

  • Author
    Sovereign 1958

Original Images

Cocconeis rugosa orig illus
Cocconeis rugosa orig descr

Cite This Page

Kociolek, P. (2011). Cocconeis rugosa. In Diatoms of North America. Retrieved July 24, 2024, from https://diatoms.org/species/cocconeis_rugosa


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