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in Corliss, 1979 Size, medium to large; shape, elongate and radially symmetrical; free-swimming; somatic ciliation, holotrichous with polar anterior suture separated from oral region and synhymenium; syn- hymenium, extending almost completely around body circumference just below level of the cyto- stome-cytopharyngeal apparatus ; cytostome in anterior 1/4 of body; macronucleus, globular to ellipsoid; micronucleus, present; contractile vacu- ole, medially located on ventral surface; feeding on diatoms, other microalgae, and cyanobacteria ; in marine, freshwater, and occasionally terrestrial habitats; two genera. – Beersena Jankowski, 1989 (for preoccupied Phasmatopsis Deroux, 1978) – Nassulopsis Foissner, Berger, & Kohmann, 1994 Family ORTHODONELLIDAE Jankowski, 1968 Size, small to medium; shape, roughly ovoid, sometimes with asymmetrical lobe or beak to the left; free-swimming; somatic ciliation, hol- otrichous; synhymenium, thickly ciliated, extending from right postoral body surface, just below level of the cytostome-cytopharyn- geal apparatus, to left preoral body surface into preoral suture, which is formed by right somatic kineties extending around anterior end onto the left side ; cytostome in anterior 1/4 of body; macronucleus, ellipsoid to elongate band- form; micronucleus, present; contractile vacuole, present; feeding on diatoms , other microalgae, and cyanobacteria ; predominantly in marine and brackish habitats; two genera and one genus incertae sedis . – Orthodonella Bhatia, 1936 – Zosterodasys Deroux, 1978 Incertae sedis in Family Orthodonellidae – Eucamptocerca da Cunha, 1914 [nomen dubium] Family SCAPHIDIODONTIDAE Deroux in Corliss, 1979 Size, small; shape, somewhat dorsoventrally flattened with slightly broader anterior end and gently tapered posterior; free-swimming; somatic ciliation, holotrichous, but reduced on much of the dorsal surface of Scaphidiodon ; synhymenium or hypostomial frange, sparsely ciliated, extending from only slightly right postoral region onto left preoral body surface into preoral suture ; cytostome in anterior 1/4 of body; macronucleus, globular to ellipsoid; micronucleus, present; con- tractile vacuole, present; feeding on diatoms , other microalgae, and cyanobacteria ; in marine and freshwater habitats; two genera. – Chilodontopsis Blochmann, 1895 – Scaphidiodon Stein, 1859 Family SYNHYMENIIDAE Jankowski in Small & Lynn, 1985 Size, medium; shape, elongate; free-swimming; somatic ciliation, holotrichous; synhymenium or hypostomial frange, extending into a left preoral suture and also with a second preoral suture to right of the first, into which synhymenium does not extend ; cytostome in anterior 1/4 of body; macronucleus, ellipsoid; micronucleus (?); con- tractile vacuole, present; feeding (?); in freshwater habitats; one genus. NOTE : This family and genus need careful redescription. – Synhymenia Jankowski, 1968 Order Nassulida Jankowski, 1967 (syns. Ambihymenida , Cyrtohymenostomatida p.p ., Parahymenostomatida , Paranassulida , Pronassulida p.p .) Size, small to large; shape, elongate, ovoid; alve- olocysts, present; somatic ciliation, holotrichous, usually dense with kineties closely adjacent; distinct preoral suture; somatic kinetosomes with a proxi- mal and distal cartwheel ; somatic extrusomes, rod-like, when present; synhymenium or hypos- tomial frange, beginning in postoral region, always to right of the stomatogenic kinety, and extending to lateral left onto dorsal surface, but sometimes reduced to 3–4 polykinetids 398 17. The Ciliate Taxa Including Families and Genera restricted to a shallow oral cavity ; cyrtos, typi- cally large, with complete palisade of nematodes- mata; cystment, common; three families. Family FURGASONIIDAE Corliss, 1979 (for Cyclogrammidae ) Size, small to medium; shape, ovoid to ellipsoid; free-swimming; somatic ciliation, holotrichous; somatic extrusomes as fusiform trichocysts; oral region in anterior 1/3 of the body with one to three left oral polykinetids and one short, right paroral in the oral area, but not confined to an oral cavity ; cyrtos, conspicuous, surrounding cytostome-cytopharynx; macronucleus, globular to ellipsoid; micronucleus, present; contractile vacu- ole, midventral; feeding on bacteria and smaller protists, including microalgae; typically in fresh- water, but sometimes terrestrial, habitats; four genera. – Furgasonia Jankowski, 1964 – Parafurgasonia Foissner & Adam, 1981 – Urliella Foissner, 1989 – Wolfkosia Foissner, Agatha, & Berger, 2002 * Family NASSULIDAE de Fromentel, 1874 (for Odontoholotrichidae ; syns. Cyrtohymen- ostomatidae , Enigmostomatidae , Liosiphonidae ) Size, small to large; shape, roughly ellipsoid; free-swimming; somatic ciliation, holotrichous, dense; synhymenium hypostomial frange, with few to many polykinetids composed of at least four kinetosomes extending from postoral region to left, sometimes onto dorsal surface ; paroral dikinetids sometimes conspicuous; cyrtos, prominent, surrounding cytostome-cytopharynx in anterior 1/3 of body; macronucleus, globular to ellipsoid; micronucleus, present; contractile vacuole, typically single, midventral; algivorous; in marine, occasionally brackish, and freshwater habitats, widespread; five genera and three genera incertae sedis . – Nassula Ehrenberg, 1834 – Nassulides Foissner, Agatha, & Berger, 2002 * – Naxella Fryd-Versavel, Iftode, & Deroux, 1980 – Obertrumia Foissner & Adam, 1981 – Rhinakis Iftode, Fryd & Deroux in Deroux, 1994 Incertae sedis in the Family Nassulidae – Archinassula Kahl, 1935 – Chilodina Srämek-Husek, 1957 – Stomatophrya Kahl, 1933 Family PARANASSULIDAE Fauré-Fremiet, 1962 (syns. Enneameronidae , Gullmarellidae ) Size, medium, typically >100 µm long; shape, ovoid to elongate-ovoid; free-swimming; somatic ciliation, holotrichous; oral region in anterior 1/4 of cell with oral structures as 3–4 polykinetids to the left of the cytostome in a shallow oral pit ; cyrtos, conspicuous; macronucleus, ellipsoid to ribbon-like; micronucleus, present; contractile vacuole, on dorsal surface; feeding (?); in marine habitats; two genera and one genus incertae sedis . – Enneameron Jankowski, 1964 (subj. syn. Nassulopsis ) – Paranassula Kahl, 1931 Incertae sedis in Family Paranassulidae – Gullmarella Fenchel, 1964 Order Microthoracida Jankowski, 1967 (syns. Cyrtopharyngina , Microthoracina , Prop- eniculida ) Size, small to medium, usually <100 µm long; shape, frequently broadly ellipsoidal, with right side more rounded, occasionally crescentic, and often laterally flattened; alveolocysts, present; pellicle, firm and rigid, with thickened epiplasm in some forms; somatic ciliation, holotrichous, but typically with a few somatic kineties, sepa- rated by wide interkinetal spaces, composed of monokinetids, dikinetids, but polykinetids in the Family Discotrichidae; somatic extrusomes as fibrous trichocysts with anchor-like tip (fibrocysts), except in Family Discotrichidae ; oral cavity, usually three left oral polykinetids, with oral cavity sometimes displaced to posterior due to differential growth of cortex; right paro- ral dikinetid, variably developed, but its ves- tige always appears in stomatogenesis ; cyrtos, small, with complete palisade of nematodesmata; often cyst-forming; microphagous and algivo- rous; typically in freshwater and terrestrial habi- tats, but Discotricha is marine; three families. 17.3 The Ciliate Taxa to Genus 399 Family DISCOTRICHIDAE Jankowski, 1967 Size, small; shape, slightly reniform; free- swimming; cortex, forming papillae distributed between somatic kineties; somatic kineties com- posed of cirrus-like polykinetids, most of more than four kinetosomes, distributed