Ehrenberg, 1831. Colourless cryptomonads, with stiff elongate-ovate body, 19 to 30 microns long. Two subequal flagella, shorter than the length of the body, insert in an anterior pocket which is surrounded by rows of extrusomes. Small extrusomes are also visible under the cell membrane. The nucleus is located posteriorly to the pocket. A contractile vacuole is located anteriorly and empties into the pocket. Cells contain refractile storage products and often two refractile Maupas bodies. Cells rotate while swimming, and can also swim backwards.