Valves are semi-lanceolate, with a convex dorsal margin. A large siliceous crest lies on the centreal dorsal face/mantle junction. The crest is narrow near the base, and expands distal to the valve. The ventral side is nearly straight or slightly concave, with a slightly tumid central margin. Valve apices are rounded and ventrally deflexed. The raphe is filiform and arcuate, with dorsally deflected proximal ends. The central area is triangular with a narrow ventral side, which may extend to the ventral margin in some specimens. Striae are parallel at the valve center, becoming radiate near the apices, occurring 13-14 in 10 µm throughout. The striae are uniseriate and composed of round areolae, occurring 18-20 in 10 µm. The dorsal mantle is curved and ornamented with stria and areola of lower density (ca. 11 in 10 µm) compared to the stria and areola density of the valve face.


Amphora calumetica has been reported as a rare taxon in Lake Michigan plankton communities (Stoermer and Yang 1969, 1971, Stoermer 1980, Edlund and Stoermer 1999). It is more common in in epipsammic communities of Lake Michigan and Lake Huron, with specimens illustrated here from nearshore Lake Superior. It has also been reported from a large oligotrophic lake in Mongolia (Levkov 2009).

Chloroplasts of A. calumetica are “H-shaped” with a strongly constricted central bridge that connects two long plastid arms that lie parallel to the dorsal margin of the each valve face. Living cells contain two prominent volutin granules located equidistant from the valve center to the apices.

Amcalumetica  Live
Credit: Image by Mark Edlund
Living cell, ventral view of A. calumetica. Epipsammon, St. Joseph, Lake Michigan.

Original Description

Amphiprora CALUMETICA, List of diatoms of Lake Michigan, B.W. Thomas. Chicago.

  • Basionym
    Amphiprora calumetica
  • Author
    B.W.Thomas ex Wolle 1890

Original Images

Amphora calumetica orig illus
Amphora calumetica orig descr

Cite This Page

Burge, D., Edlund, M. (2017). Amphora calumetica. In Diatoms of North America. Retrieved June 13, 2024, from


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