Ulnaria contracta may be confused with larger specimens of Synedra goulardii; however, S. goulardii is more constricted at the center, less linear in outline, and tapers more gradually from the center to valve apices. Ulnaria ulna is greater in length than U. contracta and has broader, less constricted ends.

LM scalebar = 10 µm
Ulnaria contracta LM2 Ulnaria contracta LM4 Ulnaria contracta LM6 Ulnaria contracta LM3 Ulnaria contracta LM1 Ulnaria contracta LM5 Ulnaria contracta LM7
Length Range
65-149 µm
Width Range
6.5-6.8 µm
Striae in 10 µm

Ulnaria goulardii

(Bréb. ex Cleve and Grunow) D.M.Williams, Potapova and C.E.Wetzel 2020

Synedra goulardi LM4 Synedra goulardi LM3 Synedra goulardi LM2 Synedra goulardi LM1 Synedra goulardi LM5 Synedra goulardi LM6 Synedra goulardi LM7
Length Range
55-103 µm
Width Range
8.5-10.5 at center; 8.6-12.4 at maximum µm
Striae in 10 µm

Also compare to

Ulnaria ulna

(Nitzsch) Compère 2001