The cells exhibit an ovoid shape or are slightly narrowed at one end, giving them a keystone- or pear-shaped appearance. They form colonies arranged in a sack-like globular structure surrounded by mucilage. Each cell is equipped with two flagella, two contractile vacuoles, and an eyespot. The chloroplast in each cell is large and cup-shaped, containing at least one pyrenoid. Asexual reproduction takes place through the simultaneous division of all cells, while sexual reproduction involves the division of each cell into 16-32 zoogametes.