Cell is covered by thick armoured plates; long, sharp horns protrude from both ends of the cell.
Thick armoured plates and horns are absent.
Cell is covered by thick armoured plates; if horns are present, these are short and blunt (cf. [Ceratium]).
![[Ceratium], Lake Rotoroa, Hamilton, X80. Photo: Otago Regional Council & Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/ceratium80__FillMaxWzMwMCwyMDBd.jpg)
![[Gymnodinium], X1000. Photo: Phil Novis, Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/gymnodinium_phil1000__FillMaxWzMwMCwyMDBd.jpg)
![[Peridinium] (sewage pond), X400. Photo: Otago Regional Council & Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/peridinium400__FillMaxWzMwMCwyMDBd.jpg)