6 (5) Some ciliary rows terminating anteriorly against a neighbor- 

 ing ciliary row. Posterior to the cytostome along this zone 

 is a ribbon of 2-3 closely set rows of short cilia 



6 (5) No such ribbon of short cilia present 8 



7 (6) Cytostome oval or circular, surrounded by cilia. 

 Family PRORODONTIDAE. 



(6) Cytostome slitlike on a nonciliated ridge offset by a groove 

 along which cilia are dense; anterior end obliquely trun- 

 cate. Family SPATHIDIIDAE. 



8 (6) Cell firm, noncontractile, barrel-shaped, with armored stavelike 

 plates in cortex, usually with spines. Several cilia emerging 

 between adjacent staves. Family COLEPIDAE. 



8 (6) Surface not as above. If firm, then only 1 cilium on each plate 9 



