Family STROMBIDIIDAE Fauré-Fremiet, 1970

Syn.	Tontoniidae

Free-swimming (rarely loricate), pelagic forms; circlet of apical membranelles "open"; somatic ciliature greatly reduced or even absent altogether; pellicle, especially in posterior half of body, made rigid by presence of both "trichites" (in a band) and polysaccharide plaques (over a broad area); perilemma present in some species; predominantly in marine habitats, with one species an ectosymbiont of echinoids, though several very common planktonic fresh-water forms.

Buehringa Busch, 1921. Few (perhaps only one) species.
Laboea Lohmann, 1908 (syn. Conocylis). Single (or more?) species.
Strombidium Claparède & Lachmann, 1859 (syn. Strombidion). Very many (ca. 50) species.
Tontonia Fauré-Fremiet, 1914. Few species.