18 (H) Ciliary rows spiraied. Fingerlike projections near cytostome. Endocommen- 

 sal in ctenophores. Pericaryon cesticola, order Trichostomatida (see Anno- 

 tated Systematic List) . 



18 iH) Not as above 19 



19 (18) Vestibulum elongate; right edge of vestibulum with a narrow dense bor- 

 der of cilia. Closely set longitudinal rows of cilia along left edge of ves- 

 tibulum. Macronucleus extensively Feulgen negative. Family GELEI- 

 IDAE. 



\J 



19 (18) Vestibulum and its cilia otherwise. 



20 (19) Vestibulum longitudinal, narrow, about one-third to one-half body length, 

 with one row of cilia. Endocommensal in sea urchins. Schizocaryum 

 dogieli, Family PLAGIOPYLIDAE. 



20 {19) Vestibulum otherwise. 



21 



21 {20) Vestibulum a pocket in posterior half of body 22 



21 {20) Vestibulum in anterior half of body 23 



12 



