Genus: Filament without branching; cell body cylindrical; one or several chloroplasts band-shaped, spirally arranged within the cell, pyrenoids present; septum with or without folded structure (Guide book to the "Photomicrographs of the Freshwater Algae", 1998). About 300 species (Illustrations of The Japanese Fresh-water Algae, 1977).
Species:
S. sp.21
3 chl. with 1/2 turns
385-535 x 28 μm
Japan, 1998
Movies 
S. sp.21b
4 straight chl.
370 x 28 μm
Japan, 1998
S. sp.21c
4 chl. with 1.5 turns
370 x 32 μm
Saitama, 1999
