44 (i3) Buccal cavity narrow; left-hand longitudinal series part of first ciliary row to left 

 of cytostome. Family COHNILEMBIDAE. 



44 (43) Buccal cavity wide. Left portion of buccal cilia a membrane 1-2 cilia wide, 

 variously segmented into 1-3 linear parts, distinct from somatic ciliary rows. 

 Family PSEUDOCOHNILEMBIDAE. 



45 (iS) Cell flat on one side with caudal projection. Endozoic in sea urchins 46 



45 (iS) Cell circular in cross section, without caudal projection. Including free-living 



and endocommensal forms 48 



46 (45) Anterior end truncate. Buccal cavity on small side, near anterior end, over- 

 hung by frontal lobe. Entorhipidium, Family ENTORHIPIDIIDAE. 



46 (45) Anterior end rounded. Buccal cavity variously located 47 



47 (46) Ciliary rows longitudinal, equidistant. Buccal cavity small in anterior one- 

 fourth of cell. Caudal projection small with 1 caudal cilium. Entodiscus, 

 order Scuticociliatida (see Annotated Systematic List). 



47 (4(5) Ciliary rows asymmetrical. Buccal cavity elongate, variously located. 

 Caudal prolongation varying in size, with one to many cilia. Crypto- 

 chilum, Cryptochilidium, order Scuticociliatida (see Annotated System- 

 atic List). 



20 



