• Category
  • Length Range
    32-95 µm
  • Width Range
    8-17 µm
  • Striae in 10 µm
  • Synonyms
    Navicula amphora Ehrenb.



Valves are semi-elliptic with a smoothly arched dorsal margin and slightly concave ventral margin. Valve ends are rounded. The axial area is narrow. An uninterrupted raphe ledge (a thin, elevated T-shaped structure that extends laterally to the raphe) is present. The raphe ledge is visible, extending the length of the cell and covering the dorsal and ventral striae near the axial area. The raphe is linear and arched dorsally. Proximal and distal raphe ends are deflected dorsally. Dorsal striae are interrupted transapically by intercostal ribs. The dorsal striae are slightly radiate centrally, becoming more radiate toward the apices. Ventral striae consist of an uninterrupted row of single areolae, slightly radiate centrally becoming convergent at the apices. A dorsal fascia is absent. A ventral fascia is present, extending to the ventral margin.

Original Description

  • Basionym
    Frustulia ovalis
  • Author
    Kütz. 1833

Original Images

Frustulia ovalis orig illus
F Ovalis Kutzing 1833 Desc

Cite This Page

Stepanek, J., Kociolek, P. (2011). Amphora ovalis. In Diatoms of North America. Retrieved May 30, 2024, from https://diatoms.org/species/amphora_ovalis


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