Body barrel-shaped, anteriorly transversely truncate; frontal plate nonciliferous. Without notch in area of oral opening. Oral cavity shallow, extending over anterior 1/3-1/2 of body. Contractile vacuole in posterior end. Bipolar ciliary rows 12-16 in number, anterior portions composed of dikinetids, posterior of monokinetids; 1 elongate caudal cilium. Adoral membranelle 1 usually composed of single row of 4-9 basal bodies, rarely with very short second row; adoral membranelle 2 composed of 2-3 basal body rows; adoral membranelle 3 formed by small patch of basal bodies. Paroral membrane on right in oral cavity, anteriorly terminating adjacent to adoral membranelle 2. Scutica consisting of few kinetosomes. Swims rapidly. Size in vivo 20-60 x 10-40 µm.
Ref.: Kahl (1931), Dragesco and Dragesco-Kernéis (1986), Petz et al. (1995a), Song and Packroff (1997).