Diatoms of North AmericaDiatoms of North America
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Compare Neidium iridis

(Ehrenb.) Cleve 1894

Compare

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.

LM scalebar = 10 µm
Neidium iridis LM4 Neidium iridis LM5 Neidium iridis LM2 Neidium iridis LM3 Neidium iridis LM6 Neidium iridis LM1
Length Range
145-261 µm
Width Range
32-37 µm
Striae in 10 µm
12-13

Neidium fossum

Lefebvre and P.Ham. 2015

Neidium fossum LM6 Neidium fossum LM5 Neidium fossum LM4 Neidium fossum LM3 Neidium fossum LM2 Neidium fossum LM1
Length Range
66.7-129.7 µm
Width Range
20.1-24.9 µm
Striae in 10 µm
17-18

Neidium amphigomphus

(Ehrenb.) Pfitzer emend. K.Lefebvre and P.B.Ham. 2015

Neidium amphigomphus LM6 Neidium amphigomphus LM5 Neidium amphigomphus LM4 Neidium amphigomphus LM3 Neidium amphigomphus LM2 Neidium amphigomphus LM1
Length Range
49.9-138.6 µm
Width Range
22-31.7 µm
Striae in 10 µm
15-16

Neidium dilatatum

(Ehrenb.) Cleve 1894

Neidium dilatatum 1 L1430 Neidium dilatatum 2 L1428 Neidium dilatatum 3 L1428 Neidium dilatatum 4 L1428 Neidium dilatatum 5 L1428 Neidium dilatatum 6 L1430 Neidium dilatatum 7 L1430
Length Range
154-231 µm
Width Range
40-49 µm
Striae in 10 µm
15-16

Also compare to

Neidium firmum

(Kütz.) Hamilton and Lefebvre 2015