Valves are broadly elliptical. The longitudinal canals are a distinctive lanceolate shape about 1/3 to 1/2 the width of the valve at center, which narrows towards the valve apices. The axial area is occupied almost completely by a broad raphe sternum that encloses the raphe. The central area is small and elliptical. Striae consist of double rows of areolae, one row may appear more prominent than the adjacent row. Striae are radiate throughout and extend onto the longitudinal canals. Areolae are distinct in LM and number 12-14 in 10 µm, but are more closely spaced over the longitudinal canals.


Diploneis finnica is a northern species. There are seven records of this species in the Montana Diatom Collection from lakes and streams in western Montana and northern Idaho. The pH of these waters ranges from 7.4 to 8.2 and specific conductance ranges from 39 to 90 µS/cm. Patrick and Reimer (1966) report Diploneis finnica from New England and the Pacific Northwest in "fresh water, particularly standing water, indifferent to small amounts of salt". As the specific epithet suggests, the type locality of this species is in Finland.

Ross Creek 3
Ross Creek, Lincoln County, northwest Montana: home of Diploneis finnica.

Original Description

  • Basionym
    Cocconeis finnica
  • Author
    Ehrenb. 1838

Original Images

Diploneis Finnica  Orig Descr

Cite This Page

Bahls, L. (2011). Diploneis finnica. In Diatoms of North America. Retrieved June 23, 2018, from


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