Extended specimens elongate cone- to trumpet-shaped, highly contractile; contracted individuals globular to pyriform. Sessile, posterior end attaches to substrate with holdfast, may detach when disturbed. Macronucleus indistinctly moniliform, composed of about 5-20 nodules. Contractile vacuole left of oral cavity, with long, posteriorly directed collecting canal. Colourless cortical granules in interkinetal rows. About 100 longitudinal somatic kineties. Adoral zone of membranelles descending in clockwise spiral into oral cavity, composed of >200 membranelles; undulating membrane paralleling adoral zone. About 50 ciliary rows on peristomial field. Specimens appear green from symbiotic algae. Length of extended specimens in vivo up to 2000 µm.
Ref.: Dragesco and Dragesco-Kernéis (1986), Foissner et al. (1992).