Cells small, hourglass shaped, with a spine at each corner.
Semi-cells rounded, often with rough or warty surface, but spines do not occur.
Semi-cells usually longer than wide, with prominent lobes, and a notch at the end of each one.
Cell flattened in end or side view; semi-cells composed of radiating "arms", all in one plane.
Semi-cells long and cylindrical (with wavy outline in some species), with swelling near constriction.
Cell not flattened; "arms" emerge from the end of each semi-cell and are radially arranged if view end-on.
Semi-cells rounded; constriction deep or wide; cell outline relatively smooth except for short spines (cf. [Cosmarium]).
Semi-cells ovoid to slightly polygonal, each ornamented by at least 4 spines arising at 90 degress to the cell surface.
![[Cosmarium], X400. Photo: Phil Novis, Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/cosmarium_phil400__FillMaxWzMwMCwyMDBd.jpg)
![[Euastrum], Ngaere wetland, X1000. Photo: Taranaki Regional Council & Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/euastrum1000__FillMaxWzMwMCwyMDBd.jpg)
![[Micrasterias], north Taranaki swamp, X400. Photo: Taranaki Regional Council & Manaaki Whenua](/assets/Tools-And-Resources/Identification/freshwater-invertebrates/micrasterias400__FillMaxWzMwMCwyMDBd.jpg)
![[Pleurotaenium], north Taranaki swamp, X100. Photo: Taranaki Regional Council & Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/pleurotaenium100__FillMaxWzMwMCwyMDBd.jpg)
![[Staurastrum], Lake Johnson, X640. Photo: Otago Regional Council & Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/staurastrum640__FillMaxWzMwMCwyMDBd.jpg)
![[Staurodesmus], Lake Rotoiti, X100. Photo: Thomas Wilding](/assets/Tools-And-Resources/Identification/algae/staurodesmus100__FillMaxWzMwMCwyMDBd.jpg)
![[Xanthidium], X400. Photo: Phil Novis, Manaaki Whenua](/assets/Tools-And-Resources/Identification/algae/xanthidium_phil__FillMaxWzMwMCwyMDBd.jpg)