No. 2.] FRESH-WATER PROTOZOA. 5/ 



One row of about seven large ventral cilia ; no sternal 

 cilia and with long border and anal cilia. . . .Belladina 



7. Body flask-shaped Platytrichotus* 



Body not flask-shaped 8 



8. With no sternal cilia Holosticha* 



With five sternal cilia and fifteen to seventeen anal 



cilia upon the left side Amphisia 



With three sternal and no anal cilia ; body narrowed 



behind Uroleptus* 



- With the two rows of ventral cilia wide apart, and 



no sternal cilia Psilotricha 



9. Five ventral cilia and two or three rows of bristle- 



like cilia on either side, of which the inner rows 



have only a few cilia Pletcrotricha* 



Three of four oblique rows of cilia, and three rows 



parallel to the peristome border Onychodromus* 



One somewhat irregular oblique row of bristle-like 



cilia and five or six sternal cilia Gastrostyla 



10. Peristome wholly lateral, very small ; usually two 



ventral cilia in front and five anal cilia. .Gonostonum 

 Eight ventral cilia and five anal* cilia at the base of 



the tail Urosoma* 



Five ventral cilia II 



11. Inner wall of peristome bent toward outer wall; 



without caudal bristles ; body usually flexible .... 



Oxytricha* 

 Inner wall of peristome bent toward the outer wall ; 



without caudal bristles; body not flexible. . . .Histrio'^ 

 Inner wall of peristome bent away from outer wall ; 



usually with three caudal bristles Stylonychia* 



12. Four border cilia at posterior end ; adoral zone sur- 



rounding the front Aspidisca* 



No border cilia ; adoral zone confined to the left side 



Euplotes* 



13. Bearing outside the adoral zone, near the middle, a 



simple or double crown of long bristles Halteria* 



Like the above but without the crown of bristles .... 



Stroinbidmm* 



