Valves are semi-lanceolate with an arched dorsal margin. The ventral margin is straight to slightly convex. Valve apices are protracted, capitate, and ventrally curved. The raphe is located near the valve midline, and is straight to slightly arched with proximal raphe ends deflected sharply toward the dorsal margin. The axial area is narrow on the dorsal side and extends nearly to the valve margin on the ventral side. A fascia is present on the dorsal side, more or less round to elliptical, 'open' on the ventral side and separated from the dorsal margin by a row of short striae. A ventral fascia is absent. A siliceous thickening is present on the dorsal valve side of the central area. Dorsal striae are punctate, and parallel to slightly radiate. Ventral striae are composed of a single row of very short areolae running continuously along the ventral margin. The Ventral striae can be difficult to resolve in the LM if the valve is tilted.


Original Description

  • Basionym
    Amphora normanii
  • Author
    Rabenh. 1864

Cite This Page

Stepanek, J. (2011). Halamphora normanii. In Diatoms of North America. Retrieved June 22, 2018, from


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