104 (83) 



Cytostome apical, 

 whorls 



104 (83) 



Cilia in circlets or spiraling 



Cytostome nonapical or ab- 

 sent. Cilia in parallel oblique 

 rows, isolated groups of rows 

 or some other arrangement. . 



106 



105 (lOi-) Cytostome on cell surface, often on a conical 

 prominence. Retractile seizing organelles in 

 some species. Cilia in circlets. Family 

 DIDINIIDAE. 



105 



105 



(104) Cytostome in apical vestibulum. 

 Family TRIMYEMIDAE. 



Cilia in spiraling whorls 



(104) Cytostome at posterior pole. Prominent spiraling undulating mem 

 brane present. Anterior group of thigmotactic cilia present. Ecto 

 ■ commensal on gills of bivalve molluscs. Family HEMISPEIRIDAE 

 in part (also see couplet 52). 



106 (104) Cell laterally compressed, with rigid pellicle. Cytostome 



and compound cilia prese- t 107 



106 (104) Cell without rigid pellicle or cytostome. All cilia simple 109 



38 



