(B) Ploimaeae; disk variable, often circular, sometimes with a lobed trochus bearing membranelles (vibratile styles); trophi complete, malleate, submalleate, virgate, or forcipate; anus subapical; foot usually short, and usually bearing two toes which may be much elongated.
I, Simple disk of Microcodon; 2, bdelloid disk of Rotifer and of most Melicertids showing dorsal gap; 3, disk of Hydatina, with lobed ridges in the groove, bearing vibratile styles (membranelles); 4, disk of Melicerta ringens and M.
In most rotifers, on the contrary, the trochus is stronger than the cingulum, often lobed, and with some of its cilia aggregated into vibratile styles homologous with the combplates of Ctenophora (q.v.) and the membranelles of ciliate Infusoria (q.v.).
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