• Category
  • Length Range
    24.9-31.7 µm
  • Width Range
    5.9-7.0 µm
  • Striae in 10 µm
    12-15 at the valve center, 16-19 near the apices
  • Reported As
    Cymbella descripta (Hein 1990, p. 33, pl. 9, fig. 6)
  • Genus Considered



Valves are weakly dorsiventral, lanceolate to elliptic-lanceolate with capitate apices deflected slightly to the ventral side. Valve shoulders are lacking. In smaller valves there is slight asymmetry on either side of the transapical axis, giving valves a somewhat gomphonemoid appearance. The axial area is narrow. The central area is small, formed by the two opposing shorter and more widely spaced central striae. The raphe is lateral with weakly inflated proximal ends that are deflected toward the dorsal margin. Distal raphe ends are hooked toward the ventral margin. Striae are radiate except at the valve center and near the apices, where they are parallel. Areolae are very fine and difficult to resolve in LM.


Encyonopsis aequaliformis has been collected from a pond and a small lake on Adak Island, Alaska (Hein 1990) and from three lakes in western Washington (Bahls 2013).

Nada  Lake 3
Credit: Ryan Davis, Adventurers and Scientists for Conservation
Nada Lake, Chelan County, Washington: type locality of Encyonopsis aequaliformis.

Original Description

Valves lanceolate to elliptic-lanceolate, not or slightly dorsiventral. Apices distinctly capitate. Valve length 25–32 μm; valve width 5.9–7.0 μm. Axial area narrow. Central area small, defined by a shortened median stria on each side. Raphe weakly lateral and nearly straight, close to the valve midline. Proximal raphe ends slightly dilated and bent toward the dorsal side. Distal raphe fissures hooked toward the ventral side. Striae moderately radiate, parallel to weakly convergent near the apices, 12–15 in 10 μm at valve center, 16–19 in 10 μm near the apices.

  • Author
    Bahls 2013
  • Length Range
    25-32 µm
  • Width
    5.9-7.0 µm
  • Striae in 10µm
    12-15 at the valve center, 16-19 near the apices

Original Images

Encyo Aequaliformis Origimag001 Cropped
Encyo Aequaliformis Origdesc001

Cite This Page

Bahls, L. (2013). Encyonopsis aequaliformis. In Diatoms of North America. Retrieved June 13, 2024, from https://diatoms.org/species/encyonopsis_aequaliformis


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