Edlund, M.,
Burge, D.
(2015).
Semiorbis.
In Diatoms of North America.
Retrieved May 01, 2026, from https://diatoms.org/genera/semiorbis?x-craft-preview=409442409a997390693ff24c7010fd6f1c96fb56f8f091fa016a63de9a54aaccecpiqubknd
Eunotioid
Semiorbis
Valves strongly lunate
Transapical, external costae
Spines on dorsal and ventral ends of costae
Valves are strongly lunate, with thick, external, transverse costae between striae. The costae often terminate in spines at the dorsal and ventral margins. A small, greatly reduced raphe is present at the poles. The raphe is typically not visible in LM. The proximal raphe ends are on the ventral margin, while the terminal fissures curve...