Compare

Frustulia bahlsii is distinct from many other large Frustulia species by the blunt, spathulate ends of the longitudinal ribs; the porte-crayon is absent. Frustulia pangaeopsis also has blunt rib ends, but differs from F. bahlsii by shorter, narrower valves with a higher stria density. Frustulia bahlsii is larger and has a lower stria density than F. rhomboides.

LM scalebar = 10 µm
Frustulia bahlsii LM3 Frustulia bahlsii LM4 Frustulia bahlsii LM5 Frustulia bahlsii LM6 Frustulia bahlsii LM7 Frustulia bahlsii LM1 Frustulia bahlsii LM2
Length Range
123-195 µm
Width Range
26-31 µm
Striae in 10 µm
longitudinal striae 19-22, transverse striae 24-25

Also compare to

Frustulia rhomboides

(Ehrenb.) De Toni

Frustulia pangaeopsis

Lange-Bert.