• Category
  • Length Range
    9-13 µm
  • Width Range
    3.8-4.2 µm
  • Striae in 10 µm
  • Synonyms
    Amphora thumensis (Mayer) Krieger 1929
    Cymbella thumensis (Mayer) Hust. 1945



Valves are broadly semi-elliptical to semi-circular, with a smoothly arched dorsal margins and convex ventral margins. Valve ends are protracted and capitate. The raphe is located near the ventral margin, straight, with proximal ends straight to slightly dorsally deflected. The axial area is narrow at the poles, widening to form a lanceolate central area. A dorsal fascia is absent. A ventral fascia is present, extending to the ventral margin. Dorsal striae are composed of a single row of areolae, parallel near the central area becoming radiate towards the poles. Ventral striae are radiate near the central area, becoming slightly convergent near the poles.

The systematic position of Halamphora thumensis was under some debate. See Kingston et al. (1980), Krammer (1980) and Levkov (2009) for a thorough discussion.


Reported in small abundances in oligotrophic lakes

Original Description

  • Basionym
    Amphora coffeaeformis var. thumensis
  • Author
    Mayer 1919

Original Images

Mayer 1919 Image
Mayer 1919 Text

Cite This Page

Stepanek, J. (2011). Halamphora thumensis. In Diatoms of North America. Retrieved May 29, 2024, from https://diatoms.org/species/halamphora_thumensis


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