The Ceratium genus is most distinguished by the characteristic arms or horns. These help the Ceratium float; but also prevent them from moving too quickly. The horns tend to be shorter and thicker in cold, salty water, and longer and thinner in less salty, warmer water.
Ceratium are covered by an armour-like cell wall or theca, composed of many textured plates, this can easily been seen on CPR samples.
In living cells Ceratium have two flagella, a transverse flagellum beats in a spiral motion, and a longitudinal flagellum pulses in waves. The grooves in which the flagella operate are prominently seen in this species.