Valves are semi-elliptical with a smoothly arched dorsal margin, ventral margin with a central tumid expansion. Valve ends are cuneate and ventrally curved. Axial area is narrow. Raphe is positioned near the ventral margin. The raphe is arched, with proximal raphe ends deflected dorsally. The dorsal fascia is distinct, square shaped and extends from the axial area to the dorsal valve margin. Ventral fascia is distinct, and longer (apically) than the dorsal fascia by the equivalent of 2-3 striae. Dorsal striae are punctate, parallel in the central area to slightly radiate at the apices. Ventral striae composed of a single row of areolae, slightly radiate in the central area becoming convergent at the apices.


Often epiphytic

Original Description

F.V. elliptical or oval; V. marked with a transverse band; striae 64 in .001'. v.v.

  • Author
    W.Sm. 1953

Original Images

Smith 1853 Fig 2 30
Smith 1853 P 20

Cite This Page

Stepanek, J. (2011). Amphora minutissima. In Diatoms of North America. Retrieved July 21, 2018, from


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