• Category
  • Length Range
    7.5-12 µm
  • Width Range
    3.9-4.6 µm
  • Striae in 10 µm



Valves are linear-elliptical. The raphe valve has a linear to linear-lanceolate axial area, which widens toward the center of the valve, and a transversely elliptical to rectangular central area. The raphe is straight, without terminal fissures. The central and terminal raphe ends are slighlty expanded. The central raphe ends curve toward opposite sides internally. The rapheless valve has a rhomboid axial area, which often sharply widens in the valve center. Striae are radiate on both valves, 27-30 in 10 µm. One row of areolae is present on the mantle of both valves. The external openings of the areolae are mostly isodiametric.


Original Description

Frustule elliptical, always strongly curved in girdle view, especially towards the broadly rounded apices; length 7-13 μm and width 3.5-5 μm. Raphe valve striae slightly radiate, shorter in the centre, usually 25-28 in 10 μm. Central area broadly rounded to elliptical, slightly asymmetrical, occupying about half of the valve width, and surrounded by 3 or 4 short striae with slightly wider interstriae. Axial area narrow, raphe straight, central nodule thickened, distal nodules indistinct. On both valves striae similar in density, areolae unresolvable (in LM). Rapheless valve striae short, more so in the central area; axial area short, extending into a large approximately rhomboidal central area, about half the valve width, faintly grooved in the mid-line.

  • Basionym
    Achnanthes scotica
  • Author
    Flower and Jones 1989
  • Length Range
    7-13 µm
  • Width
    3.5-5 µm
  • Striae in 10µm

Original Images

Orig Ill
Orig Descr001 1

Cite This Page

Potapova, M. (2010). Psammothidium scoticum. In Diatoms of North America. Retrieved May 18, 2024, from https://diatoms.org/species/psammothidium_scoticum1


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