Navicula lundii may be difficult to distinguish without having a size range of specimens. It differs by having a transapically expanded central area, denser lineolae, and slightly subrostrate apices.
Navicula eileeniae has more rounded apices and and central striae that are slightly curved.
Navicula notha 
has slender valves, drawn-out apices, and slightly larger elliptic or rhombic central area.
Navicula parablis
has slightly set-off apices, an expanded central area, and lineolae resolved in LM.
Navicula radiosafallax has linear to linear-lanceolate valves, a lanceolate central area and slightly coarser striae.
Navicula menisculus has wider valves, coarser striae, and coarser lineolae.
Navicula cyrptotenelloides has smaller valves and a higher stria density.
Navicula irmengardis
has valves with higher length to width ratio, central area that is continuous with axial area and curved proximal raphe ends.

LM scalebar = 10 µm
Length Range
15-40 µm
Width Range
4.8-6.8 µm
Striae in 10 µm
14-16
Navicula cryptotenella LM9
Navicula cryptotenella LM8
Navicula cryptotenella LM1
Navicula cryptotenella LM4
Navicula cryptotenella LM3
Navicula cryptotenella LM7
Navicula cryptotenella LM2
Navicula cryptotenella LM9 Navicula cryptotenella LM8 Navicula cryptotenella LM1 Navicula cryptotenella LM4 Navicula cryptotenella LM3 Navicula cryptotenella LM7 Navicula cryptotenella LM2

Navicula lundii

E.Reichardt 1985

Length Range
22-38 µm
Width Range
4.8-6.9 µm
Striae in 10 µm
14-18
Navicula lundii LM7 Navicula lundii LM6 Navicula lundii LM5 Navicula lundii LM4 Navicula lundii LM3 Navicula lundii LM2 Navicula lundii LM1

Navicula eileeniae

Potapova and Ciugulea 2019

Length Range
17.8–26.5 µm
Width Range
4.2–5.4 µm
Striae in 10 µm
14-15
Navicula eileeniae LM1 Navicula eileeniae LM2 Navicula eileeniae LM3 Navicula eileeniae LM4 Navicula eileeniae LM5 Navicula eileeniae LM6 Navicula eileeniae LM7

Navicula notha

J.H.Wallace 1960

Length Range
18.7-39.3 µm
Width Range
4.1-5.5 µm
Striae in 10 µm
14-17
Gs013091 7 Navicula notha LM3 Navicula notha LM1 Drbc0032 8 Drbc0032 17 Navicula notha LM2 Navicula notha LM4

Also compare to

Navicula radiosafallax (invalid)

Lange-Bert.

BioData Reference
Lange-Bertalot 2001 Pl 22 Fig 10-13

Navicula menisculus

Schumann

BioData Reference
Lange-Bertalot 2001 Pl 12 Fig 1-7

Navicula cryptotenelloides

Lange-Bert.

BioData Reference
Lange-Bertalot 2001 Pl 26 Fig 8-16

Navicula menisculus var. obtusa

Hust.

BioData Reference
Simonsen 1987 Pl 329 Fig 25 26

Navicula parablis

M.H.Hohn and Hellerman

BioData Reference
Hohn and Hellerman 1963 Pl 3 Fig 17

Navicula irmengardis

Lange-Bert.