Fam. 16. Dinocharididae: Dinocharis E., Scaridium E., Stephanops E.
Fam. 17. Salpinidae: Salpina E., Diaschiza G., Ploesoma Herrick, Diplax G., Diplois G.
Fam. 18. Euchlanididae: Euchlanis E., Dapidia G., Apodoides Joseph.
Fam. 19. Cathypnidae: Cathypna G., Distyla Eckstein, Monostyla E.
Fam. 20. Coluridae: Colurus E., Metopidia E., Monura E., Mytilia G., Cochleare G., Dispinthera G.
Fam. 21. Pterodinidae: Pterodina E., Pompholyx G.
Fam. 22. Brachionidae: Brachionus E., Noteus E., Schizocerca Daday.
Fam. 23. Anuraeidae: Anuraea E., Notholca G., Eretmia G.
The group includes a number of very minute forms, besides others conspicuous both for size and beauty. A soft dorsal flap above the head occurs in Stephanops; also in Coluridae, a large family of minute species, where the flap is movable, and looks in profile like a hook overhanging the forehead. The genus Pterodina, like Pedalion and Triarthra, combines a Bdelloid disc with malleoramate trophi, while its exsertile wrinkled foot ends in a ciliated cup like that of a larval tubicolous species.
Brachionus, a large, often flat, transparent form, with a long wrinkled foot, is a very common genus, known to the earlier observers, and repeatedly figured by them. Pompholyx has a sack-like lorica, no foot, and carries its immense egg suspended by an elastic thread from the cloaca. The Anuraeidae lack the foot, and often have great spines or bristles projecting from the lorica, which no doubt facilitate floating. They are abundant in the "plankton" or floating fauna of large lakes far from the shore. Many marine species belong to this family.