Compare Neidium iridis
Neidium dilatatum is distinguished by an elliptic valve outline and multiple (5+), small longitudinal canals. Neidium firmum is much smaller and more narrow.
Large specimens of N. amphigomphous may overlap in size with the smallest specimens of N. iridis. Neidium amphigomphous, however, has distinctly acute, apiculate apices and areolae that become transapically elongate near the valve margin.
Neidium fossum has 2-3 longitudinal lines, subacute apices, and smaller size.
Neidium rugosum bears longitudinal ridges along the axial area, and smaller size.
LM scalebar = 10 µm
Length Range
145-261 µm
145-261 µm
Width Range
32-37 µm
32-37 µm
Striae in 10 µm
12-13
12-13
Length Range
66.7-129.7 µm
66.7-129.7 µm
Width Range
20.1-24.9 µm
20.1-24.9 µm
Striae in 10 µm
17-20
17-20
Length Range
49.9-138.6 µm
49.9-138.6 µm
Width Range
22-31.7 µm
22-31.7 µm
Striae in 10 µm
15-16
15-16
Length Range
154-231 µm
154-231 µm
Width Range
40-49 µm
40-49 µm
Striae in 10 µm
15-16
15-16
Length Range
81.8-154.6 µm
81.8-154.6 µm
Width Range
21.9-29.9 µm
21.9-29.9 µm
Striae in 10 µm
16-18
16-18
