Compare

Neidium kozlowii has wider apices, a narrow axial area, and lacks the depressions along the raphe and in the central area. Neidium bobmarshallensis, N. fogedii, and N. inconstans have smaller valves with different shapes and higher stria densities.

LM scalebar = 10 µm
Neidium undulatum LM5 Neidium undulatum LM1 Neidium undulatum LM2 Neidium undulatum LM3 Neidium undulatum LM4
Length Range
82-110 µm
Width Range
23-26 µm
Striae in 10 µm
10-12

Neidium bobmarshallensis

L.L.Bahls 2013

Neidium bobmarshallensis LM1 Neidium bobmarshallensis LM2 Neidium bobmarshallensis LM3 Neidium bobmarshallensis LM4 Neidium bobmarshallensis LM5
Length Range
60-79 µm
Width Range
14.8-17.8 µm
Striae in 10 µm
13-15

Neidium fogedii

L.L.Bahls 2013

Neidium fogedii LM6 Neidium fogedii LM5 Neidium fogedii LM4 Neidium fogedii LM3 Neidium fogedii LM2 Neidium fogedii LM1
Length Range
33-55 µm
Width Range
9.3-11.1 µm
Striae in 10 µm
17-18

Also compare to

Neidium kozlowii

Mereschk. 1906