• Category
  • Length Range
    8.7-18.7 µm
  • Width Range
    2.7-3.6 µm
  • Striae in 10 µm



Valves not dorsiventral, lanceolate to linear-lanceolate with broadly rounded subrostrate to subcapitate apices that are not obviously deflected. The axial area is very narrow, subcentral to slightly ventrally placed. The central area is small, rounded and asymmetric, more developed on the dorsal side. The raphe is filiform. Proximal raphe ends are deflected slightly toward the dorsal side. Terminal raphe fissures are hooked toward the ventral side. Striae are weakly radiate, becoming parallel and a bit closer together near the apices.


Encyonopsis bobmarshallensis has been collected from two oligotrophic alpine lakes along the Continental Divide in the Bob Marshall Wilderness of western Montana (see photos below). The water quality of these lakes is unknown.

Dean Lakesummitpostorg
Credit: Summitpostorg
Dean Lake, Bob Marshall Wilderness, Montana
Trilobite Lakesfrom Trilobite Peaksummitpostorg
Credit: summitpost.org
Trilobite Lakes, Bob Marshall Wilderness, Montana. Upper Trilobite Lake (right) is the type locality of Encyonopsis bobmarshallensis.

Original Description

Valves lanceolate to linear-lanceolate, slightly dorsiventral. Apices rostrate to subcapitate. Valve length 8.7–18.7 µm; valve width 2.7–3.6 µm. Axial area very narrow. Central area small, but distinct. Raphe filiform. Proximal raphe ends not inflated, deflected dorsally. Distal raphe fissures curved toward the ventral side. Striae weakly radiate, 22–24 in 10 µm.

  • Author
    Bahls 2013
  • Length Range
    8.7-18.7 µm
  • Width
    2.7-3.6 µm
  • Striae in 10µm

Original Images

Encyonopsis bobmarshall orig illus
Encyo Bobmarshall Origdesc002

Cite This Page

Bahls, L. (2013). Encyonopsis bobmarshallensis. In Diatoms of North America. Retrieved July 13, 2024, from https://diatoms.org/species/encyonopsis_bobmarshallensis


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