Compare

Asterionella formosa has coarse striae with a capitate foot pole and a rounded head pole. Asterionella ralfsii and A. ralfsii var. hustedtiana have rounded head poles and larger mid-valve widths.

LM scalebar = 10 µm
Asralf Amer  Mbe725B 3460 192 2 Asralf Amer  Mbe725B 3001 166 7 Asralf Amer  Mbe725B 2961 164 5 Asralf Amer  Mbe725B 2800 155 5 Asralf Amer  Mbe725B 2461 136 7 Asralf Amer  Mbe725B 1884 104 6
Length Range
104.6-192.2 µm
Width Range
1.5 to 2.8 at the valve center 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
24-28

Also compare to

Asterionella ralfsii var. hustedtiana

Körner

Asterionella ralfsii

W.Sm.