Differentiation from Psammothidium altaicum and P. rechtense can be difficult. The raphe valves of P. rossii have a narrow, rectangular central area, while P. rechtense has a lanceolate central area and P. altaicum has an elliptic central area. In general, rapheless valves of P. rossii have a more narrow axial area than P. altaicum, but distinguishing rapheless valves of P. rossii and P. rechtense may not be possible. Psammothidium subatomoides has a bow-tie central area, rounded apices and the frustule is not flexed. Psammothidium biorettii is larger and has a larger central area. The raphe valve of Eucocconeis lapponica has a larger, asymmetric central area.

LM scalebar = 10 µm
Psammothidium rossii LM6 Psammothidium rossii LM4 Psammothidium rossii LM1 Psammothidium rossii LM7 Psammothidium rossii LM5
Length Range
9.7-11 µm
Width Range
4.8-5.7 µm
Striae in 10 µm

Psammothidium subatomoides

(Hust.) Bukht. and Round 1996

Psammothidium subatomoides LM10 Psammothidium subatomoides LM2 Psammothidium subatomoides LM4 Psammothidium subatomoides LM6 Psammothidium subatomoides LM8
Length Range
5.5–11 µm
Width Range
3.2-6.0 µm
Striae in 10 µm

Psammothidium bioretii

(Germain) Bukht. and Round 1996

Psammothidium bioretii LM3 Psammothidium bioretii LM2 Psammothidium bioretii LM1 Mo000019 1A Ed 3 Mo000019 1B Ed Gs028733  Psbio 1A Ed Gs028733  Psbio 1B
Length Range
12-26 µm
Width Range
5.3-9.1 µm
Striae in 10 µm

Also compare to

Eucocconeis lapponica

BioData Reference
Simonsen 1987 Pl 123 Fig 1-10

Psammothidium altaicum

(V.S.Poretzky) Bukht. in Bukht. and Round

BioData Reference
Krammer and Lange-Bertalot 2/4 Pl 20 Fig 24-32

Psammothidium rechtense

(Leclercq) Lange-Bert.