Asterionella formosa and A. ralfsii var. americana have heteropolar valves. Diatoma moniliformis has elliptic valves with rounded apices. Diatoma tenuis has more widely spaced costae and more closely spaced striae.

LM scalebar = 10 µm
Distrionella incognita LM1 Distrionella incognita LM2 Distrionella incognita LM3 Distrionella incognita LM4 Distrionella incognita LM5 Distrionella incognita LM6 Distrionella incognita LM7
Length Range
28-76 µm
Width Range
1.9-2.9 µm
Striae in 10 µm

Asterionella formosa

Hassall 1850

Ill2011 12  A Formosa2 Ill2011 12  A Formosa4 Ill2011 12  A Formosa6 Ill2011 12  A Formosa5 Ill2011 12  A Formosa1 Ill2011 12  A Formosa3
Length Range
45-68 µm
Width Range
1.1-4.5 µm
Striae in 10 µm

Diatoma moniliformis

Kütz. 1833

Diatoma moniliformis LM4 Diatoma moniliformis LM3 Diatoma moniliformis LM5 Diatoma moniliformis LM1 Diatoma moniliformis LM2
Length Range
10–40 µm
Width Range
2.5-6.0 µm
Striae in 10 µm

Diatoma tenuis

C.Agardh 1812

Diatoma tenuis LM7 Diatoma tenuis LM6 Diatoma tenuis LM4 Diatoma tenuis LM5 Diatoma tenuis LM1 Diatoma tenuis LM3 Diatoma tenuis LM2
Length Range
20-85 µm
Width Range
2.9-4.9 µm
Striae in 10 µm

Also compare to

Asterionella ralfsii

BioData Reference
Krammer and Lange-Bertalot 2/3 Pl 104 Fig 1-8