Ciliophora 397 



The peristomial area is large and more or less triangular in many 

 species, but is reduced in size and fairly narrow in others. In some cases 

 the right margin of the peristome is extended toward the left as a flange 

 ("oral lip") which partially encloses the peristome ventrally. Such a de- 

 velopment increases the efficiency of the peristome, especially in species 

 which feed on bacteria. 



Fig. 7. 39. A, B. Aspidisca turrita (Ehrbg.) Clapar^de and Lachmann, 

 lateral and ventral views, x765 (after Wang and Nie). C. Certesia quadri- 

 nudeata Fabre-Domergue, specimen 90/i long (after Kahl). D. Aspidisca 

 polystyla Stein, x840 (after Wang and Nie). E, F. Uronychia heinrothi 

 Buddenbrock, ventral view showing the peristomial membranes, and dorsal 

 view of the three postero-dorsal cirri; x200 (after Bullington). G. Euplo- 

 taspis cionaecola Chatton and Seguela, 60-70^ long; from branchial cavity 

 of ascidians (after C. & S.). H, I. Euplotidium agitatum Noland: ventral 

 view, x600; anterior end showing bases of membranelles, x450 (after N.). 



