• Category
  • Length Range
    28-48 µm
  • Width Range
    13.5-17 µm
  • Striae in 10 µm
  • Synonyms
    Surirella biseriata f. amphioxys (W.Sm.) Hust.
  • Reported As
    Surirella moelleriana (Grunow (Hustedt 1930, pg. 435, fig. 842))



Valves have a length to width ratio between 2 and 3. The keel is low and no alar wings are visible. Valves are isopolar with cuneate apices and straight, parallel sides. The valve face is strongly undulate (structures termed "porcae"). These porcae appear as rectanglar structures in the LM. Each porca is 2-3 µm wide by 4-5 µm long and is traversed by 3-4 costae, with1-2 costae between each porca. Costae are 16-20 in 10 µm, extending from the margin to the apical axis, where they meet the axial line. Four to five rows of round areolae occur between the costae, visible only in the SEM. A distinct, flat central area occurs about the axial line. Around the valve margin are what appear to be large areolae in the LM, but in the SEM these “areolae” are actually indentations in the valve face corresponding to fibulae in the interior of the valve. Areolae on the surface of the indentations directly beneath the keel penetrate to the mantle. Indentations, or portulae occur on the mantle face, corresponding to those on the valve face.


Original Description

Surirella amphioxys, n. sp. F. V. linear; V. elliptical-lanceolate, extremities subactute; canaliculi 9 in .001". Length of frustule .0012". Breadth of valve .0005". v.v.

Fresh water. Haverfordwest, August 1855, Mr. Okeden

  • Author
    W.Sm. 1856
  • Length Range
    30.5 µm
  • Width
    12.7 µm

Original Images


Cite This Page

English, J. (2011). Surirella amphioxys. In Diatoms of North America. Retrieved May 20, 2024, from https://diatoms.org/species/surirella_amphioxys


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