Suborder (1) Apostomatina Chatton & Lwoff, 1928

Syns.

Cyrtostomatina, Gemmotomina, Incitophorina

With characteristics of order s.s. (above); commonly in marine, occasionally fresh-water, crustacean hosts (members of one genus are symbionts of other apostomatines; and an atypical family is found in polychaete annelids).

With characteristics of the suborder s.s. (above); exceptional genera are Ophiuraespira in ophiuroid echinoderms, Pericaryon in ctenophores, and Phtorophrya on other apostomatines.	Family FOETTINGERIIDAE Chatton, 1911
Body of trophont pear-shaped, ciliation holotrichous; no cytostome, no rosette; tomite very small, with area of strongly thigmotactic cilia; single caudal cilium; large, partially coiled macronucleus; found in lateral caeca of digestive tube in polychaete annelids.	Family CYRTOCARYIDAE n. fam.