Cell outline crescent-shaped (lunate) with green contents.
Cell outline elongated with basal holdfast; usually attached to another object.
Cell outline has a deep constriction that divides the cell into two approx. equal semicells.
Cell wall is smooth, cell outline round to ellipsoidal, and featureless.
Cell outline long and thin (may be somewhat curved), with green cell contents.
Cell wall has the form of a rigid clear box: either semi-rectangular "shoe-box" like, or circular "hat-box" like, with fine ornamentation...
Cell wall ornamented with spines, but lacking central constriction.
Cell with rigid cell wall, lacking shallow groove at equator, and motile, propelled by one or more waving hair-like strutures (flagella).
Shallow groove encircles the cell equator.
Cell outline continually changing due to flexible cell wall (pellicle; euglenoids); may be propelled by flagella.
![[Closterium], Mill Creek, X200 . Photo: Otago Regional Council & Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/closterium200__FillMaxWzMwMCwyMDBd.jpg)
![[Characium], Welcome Creek, north Otago, X640. Photo: Otago Regional Council & Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/characium640__FillMaxWzMwMCwyMDBd.jpg)
![[Xanthidium], X400. Photo: Phil Novis, Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/xanthidium_phil__FillMaxWzMwMCwyMDBd.jpg)
![[Cyanothece], X1000. Photo: Phil Novis, Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/cyanothece_phil1000__FillMaxWzMwMCwyMDBd.jpg)
![[Closteriopsis] (sewage pond), X640. Photo: Otago Regional Council & Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/closteriopsis640__FillMaxWzMwMCwyMDBd.jpg)
![[Cerataulina], lower Taieri River, X320. Photo: Otago Regional Council & Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/cerataulina320__FillMaxWzMwMCwyMDBd.jpg)
![[Ceratium], Lake Rotoroa, Hamilton, X160. Photo: Otago Regional Council & Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/ceratium160__FillMaxWzMwMCwyMDBd.jpg)
![[Phacus] (sewage pond), X400. Photo: Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/phacus400__FillMaxWzMwMCwyMDBd.jpg)
![[Gymnodinium], X1000. Photo: Phil Novis, Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/gymnodinium_phil1000__FillMaxWzMwMCwyMDBd.jpg)
![[Euglena] (sewage pond), X640. Photo: Otago Regional Council & Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/euglena640__FillMaxWzMwMCwyMDBd.jpg)