Melosira dendrophila has spines grouped in marginal clusters, separated by porefields. Orthoseira johansenii has a larger central area with fine, weakly organized striae and spines separated by 2-4 striae.

LM scalebar = 10 µm
Orthoseira roeseana LM1 Orthoseira roeseana LM2 Orthoseira roeseana LM3 4 674 30 6  Ortho Roes 715 A 5Rep 491 22 3  Ortho Roes 715 A
22.1-50.5 µm
Striae in 10 µm
6.4-7.1 based on circumferential density

Also compare to

Melosira dendrophila

(Ehrenb.) R.Ross and P.A.Sims

Orthoseira johansenii

R.L.Lowe and Kociolek