Psammothidium scoticum

(Flower and Jones) Bukht. and Round 1996      Category: Monoraphid
BASIONYM: Achnanthes scotica Flower and Jones 1989

Psammothidium pennsylvanicum


Psammothidium semiapertum

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova - August 2010
Length Range: 8-12 µm
Width Range: 3.9-4.6 µm
Striae in 10 µm: 27-30


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

Basionym: Achnanthes scotica
Author: Flower and Jones 1989
Length Range: 7-13 µm
Width Range: 3.5-5 µm
Striae in 10 µm: 25-28

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.

Original Images

Cite This Page:
Potapova, M. (2010). Psammothidium scoticum. In Diatoms of the United States. Retrieved April 22, 2018, from

Species: Psammothidium scoticum

Contributor: Marina Potapova

Reviewer: Sarah Spaulding


Bukhtiyarova, L. and Round, F. E. (1996). Revision of the genus Achnanthes sensu lato. Psammothidium, a new genus based on Achnanthidium marginulatum. Diatom Research 11: 1-30. 10.1080/0269249X.1996.9705361

Flower, R.J. and Jones, V.J. (1989). Taxonomic descriptions and occurrences of new Achnanthes taxa in acid lakes in the U.K. Diatom Research 4(2): 227-239. 10.1080/0269249X.1989.9705072

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Psammothidium scoticum CAS

North American Diatom Ecological Database (NADED)

NADED ID: 186017

Autecology Discussion