Stein, 1859
Body generally large to very large, sometimes highly contractile. Oral ciliature conspicuous, adoral zone composed of many membranelles and often extending out of oral cavity onto and/or around anterior end of body. One or more undulating membranes on right. Somatic ciliation frequently holotrichous, with regular, even dense rows of cilia. Postciliodesmata common and prominent. Toxicysts and trichocysts absent. Fission usually isotomic. Conjugation temporary, isogamontic. Widely distributed, free-living and symbiotic.
Suborder Heterotrichina
Family Spirostomidae
Family Condylostomatidae
Family Stentoridae
Family Peritromidae
Suborder Licnophorina
Family Licnophoridae