• Category
  • Length Range
    47-54 µm
  • Width Range
    12.1-13.5 µm
  • Striae in 10 µm
  • Reported As
    Navicula rhyncocephala (Patrick & Reimer 1966)



Valves are broadly lanceolate to elliptic-lanceolate. Ends are narrow, abruptly protracted and subcapitate to capitate. The axial area is narrow and nearly linear. The central area is large and transversely elliptical. Raphe branches are weakly lateral. The proximal raphe ends are expanded and deflected slightly to the primary side. Striae are radiate and more widely spaced about the central area, becoming parallel and finally convergent at the poles. Areolae are coarse and number 20-23 in 10 µm.

Note that the specimen illustrated as N. rhynchocephala in Patrick & Reimer (1966) corresponds to the type of N. rhynchotella.


There are eight records of Navicula rhynchotella in the Montana Diatom Collection, all of them from the Poplar River or tributaries of the Poplar River in extreme northeastern Montana (near the border with Saskatchewan), where the species is uncommon. The Poplar River and tributaries are freshwater streams but with elevated levels of dissolved solids. Common diatom associates of Navicula rhynchotella in these waters include Planothidium engelbrechtii, Nitzschia commutatoides, Navicula cryptocephaloides, Navicula integra, Craticula riparia, Placoneis placentula, Navicula slesvicensis, Craticula buderi, Placoneis clementis, Navicula associata, Nitzschia bulnheimiana, Navicula amphiceropsis, and Luticola nivalis. Lange-Bertalot (2001) reports Navicula rhynchotella as widespread in Europe, in brackish waters along the coasts, in electrolyte-rich inland waters, and rarely in well buffered, alkaline freshwaters with average electrolyte content (e.g., the Rhine River).

Poplar  River
Credit: Loren Bahls
Poplar River on the Northwestern Great Plains in Montana: home of Cymbella lanceolata

Original Description

Valvae late ellipticae finibus distincte rostratis, 35-60(80) microns longae, semper magis quam 9 microns, i.e. 10-16 plerumque 13-14 microns latae. Areae et positus et numerus striarum (8-11/10 microns) et numerus lineolarum (20-25/10 microns) N. rhynchocephala similes. Structurae ultramicroscopicae significantes et differentes se praestant in imaginibus figurarum no. 63: 1-6. Comparatio photographica meliorem facet quam per multa vocabula.

  • Author
    Lange-Bert. 1993
  • Length Range
    35-60 µm
  • Width
    13-14 µm
  • Striae in 10µm

Original Images

Nrhynchotella Origimage
Nrhynchotella Origdesc

EMAP Assessment

EMAP Distribution

Navicula Rhynchotella 40
Map 40

Response Plots

Navicula Rhynchotella

Cite This Page

Bahls, L. (2011). Navicula rhynchotella. In Diatoms of North America. Retrieved June 24, 2018, from https://diatoms.org/species/navicula_rhynchotella


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