Suborder (1) Nassulina Jankowski, 1967

Syns.

Cyrtohymenina, Paranassulina

With characteristics of order s.s. (above); body typically large and cylindrical, with holotrichous ciliation; fresh-water and marine forms, with filamentous algae common as food; pellicle highly distensible.

Body roughly ellipsoidal, uniformly ciliated; hypostomial frange short but multiple, often extending along preoral suture; prominent cytopharyngeal apparatus; contractile vacuole pore single, midventral; algivorous forms, widespread in fresh-water and occasionally brackish and marine habitats.	Family NASSULIDAE de Fromentel, 1874
Body ovoid to elongate-ovoid, uniformly ciliated; hypostomial frange restricted to 3-4 "pseudomembranelles" in oral atrium surrounding cytostome-cytopharyngeal complex s.s.; preoral suture entirely separate; contractile vacuole pore on dorsal surface; found solely in marine habitats.	Family PARANASSULIDAE Fauré-Fremiet, 1962
Body ovoid to ellipsoidal, uniformly ciliated; hypostomial frange appearing as four definitive organelles in atrial area, reminiscent of buccal ciliature in oligohymenophorans; prominent cytopharyngeal apparatus; contractile vacuole pore midventral in location; fusiform trichocysts reported; typically in fresh-water habitats.	Family FURGASONIIDAE Corliss 1979