Cell(s) divided into two regions by a groove encircling the cell. May have a visible outer “armor” composed of closely adjacent plates. Cell shape (usually) roughly spherical or oval; may be tapered/pointed at one end; may have several long horn-like extensions. Cell content (usually) golden, golden-brown, or dark brown. (Usually) Unicellular. With one visible flagellum; flagellum is long and extends outward from the cell. Free-swimming; may be observed swimming in a forward spiraling or whirling style.

Cell(s) not as described to the left.