Chloroplasts visible inside cells are brown; cells are box-like and may be semi-rectangular (visible when filament bends) - chain-forming diatoms
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Melosira varians -
Valve face outline is narrow and elongated, with a pronounced swelling in the middle and smaller swellings at the ends; striae meet the edge of a very narrow sternum; although single cells may be encountered, presence of zig-zag chains almost certain.
Tabellaria flocculosa -
Boat-shaped to elongate in valve face outline; striae meet edge of central sternum; although single cells may be encountered, presence of long, ribbon-like colonies almost certain.
Fragilaria -
Boat-shaped in valve view, with prominent ribs (costae) running across the valve face, also visible in girdle view; single cells may be encountered, but commonly forms long chains.
Diatoma -
Aulacoseira granulata -
Cells drum-shaped; radiating lines absent from valve face; may be joined weakly at the edges of the valves to form chains.
Cerataulina -
Boat-shaped in valve view; raphes on only one valve, the other valve lacking a central space between the striae; single cells may be encountered, but commonly forms chains.
Achnanthes cf inflata