Unicellular chlorophyte with flattened, triangular, square or polygonal cells. A single green chloroplast fills the cell. Spines of varying length often emanate from the corners.
Found in the plankton of lakes and ponds including sewage ponds
![[Tetraedron] (sewage pond), X400. Photo: Otago Regional Council & Manaaki Whenua Image](/assets/Tools-And-Resources/Identification/algae/tetraedron400b__ScaleWidthWzEwMjRd.jpg)