• Category
  • Length Range
    15.5-60 µm
  • Width Range
    6.5-12 µm
  • Striae in 10 µm
  • Synonyms
    Surirella ovalis var. angusta (Kütz.) Van Heurck
    Surirella ovata var. angusta (Kütz.) A.Cleve
    Surirella ovalis var. angusta (Kütz.) Gutw.



Frustules have length to width ratios between 2 and 5. The valve face is flat, isopolar, with cuneate or occasionally capitate apices. In valves beyond 25 µm in length, the sides are straight and parallel, while under 25 µm the frustule can be elliptical. The keel is not raised and no alar wings are visible. Fibulae are present on the interior of the valve surface, 7-8 in 10 µm., Every third or fourth costae on the valve surface is either raised or lowered from the plane of the other costae. These altered costae correspond to the fibulae below the valve surface. Not infrequently, raised costae can arise in double form, where no intermediate lower costae exist. The striae, visible in the SEM, consist of 2-5 rows of areolae situated between the costae, 23-28 in 10 µm. Indentations in the valve face are present around the circumference of the valve are present, having the appearance of large areolae.


Original Description

S. minuta lineari-oblonga, a latere primario rectangula, secundario utroque fine aequaliter rotundata, margine subtiliter striata; striis in 1./100''' 11. Lange bis 1/50'''.

  • Author
    Kütz. 1844
  • Length Range
    45 µm
  • Striae in 10µm
    5 (probably fibulae)

Original Images

Surangusta  Orif Ill
Kutzing Type001

EMAP Assessment

EMAP Distribution

Surirella Angusta 40 Copy
Map 40

Response Plots

Surirella Angusta Copy

Cite This Page

Potapova, M, and English, J. (2010). Surirella angusta. In Diatoms of North America. Retrieved August 18, 2018, from https://diatoms.org/species/surirella_angusta


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