• Category
  • Length Range
    154-388 µm
  • Width Range
    35-58 µm
  • Striae in 10 µm
  • Reported As
    Stauroneis acuta var. terryana (Tempère 1894, pg. 150)
    Stauroneis acuta var. maxima (Peragallo 1908, pg. 87, Fig 159)



Valves are rhombic-lanceolate and very slightly gibbous in the middle. The initial valves have a more conspicuous bulge in the middle part than vegetative cells. The valve ends are acute, with large and thick pseudosepta. The raphe is straight with external slit slightly curved in the proximal part. The terminal raphe fissures are straight. The axial area varies in width from 7 - 10 µm. The stauros widens toward the valve margins. The striae are radiate and interrupted at the valve margin by a thick hyaline area that bears irregular areolae. There are 9—12 areolae in 10 µm along the striae. External areolae openings are round or transapically elongated. The areola openings adjacent to the axial area are more elongated than the others. Girdle bands have prominent septa and one row of pores.

Internally, there are two thick ridges on both sides of the raphe running almost the whole length of the valve but ending before reaching the stauros. The central ends of the internal raphe slits are straight. Areolae openings are transapically oriented slits.


Stauroneis terryi was originally described from a small wetland-stream in Connecticut, but other records are from lakes in the northeastern North America. It was more abundant in recent past compared to modern times and is probably lost from many localities that it occupied two to three hundred years ago.

Original Description

Stauroneis terryi D. B. Ward (ined.)
Frustule fuiform, slightly arcuate in girdle view, the upper valve more convex than the lower. Valves dissimilar, the upper partly enclosing the lower. No girdle bands, the valves held in place by a broad external silicious ring at the middle part. Ring slightly cemented to the valves, easily detached, about one-eighth the length of the frustules, very thin, surface obscurely punctate. Upper valve 370-400 µ long, 55-60 µ broad. Strongly convex transversely, swollen at the middle, diminishing with concave outlines to long, bluntly rounded apices, and bearing a large oval depression toward each end wherein the raphe terminates in a fine waved line; axial hyaline area rectilinear, expanding spatulately around subterminal depressions. Lower valve slightly smaller in all dimensions, without subterminal depressions, apices more slender, with lumen formed by a conspicuous thickening of the inner terminal margin; raphe continued approximately to end of valve; hyaline area rectilinear to the lumen, then narrowing almost to a point. Stauros on both valves widening outward. Striae 12 in 10 µ, nearly normal to periphery throughout, puctae becoming coarser and striae more sparse around ends of upper valve.

Fresh water. Fossil and recent.
Fall Mountain, Conn. W.A. Terry, 1890.

  • Author
    D.B. Ward ex T.C. Palmer 1910
  • Length Range
    370-400 µm
  • Width
    55-60 µm
  • Striae in 10µm

Original Images

Stauroneis Terryi Orig Ill
Stauroneis Terryi Orig Descr

Cite This Page

Potapova, M. (2022). Stauroneis terryi. In Diatoms of North America. Retrieved June 19, 2024, from https://diatoms.org/species/stauroneis-terryi


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