340 Illinois State Laboratory of Natural History. 



RHABDOSTYLA Kent. 



Similar to Epistylis, but not forming colonies. 



Several undetermined species of this genus were found on 

 various Entomostraca, on a rotifer (Polyarthra platyptera), 

 and on small aquatic worms. 



Opercularia Goldf. 



Forming colonies as in Epistylis, individuals more or 

 less narrowed at the anterior end, peristome not laterally 

 expanded ; adoral disc very strongly elevated, while the sur- 

 rounding peristomal ring is deeply excavated and the vesti- 

 bule conspicuously wide and very deep ; the adoral disc is 

 therefore borne upon a column, on which it is usually 

 obliquely placed, looking like a ciliated lid to the anterior end. 



86. O. nutans Ehkbg. 



Found in May on a Planorbis from Quiver Lake at C. 



87. O. rugosa Kell. ('84). 



Common among vegetation ; a few found in bottom towing 

 in Quiver Lake. Observed in May and July in the river and 

 in Quiver and Thompson's Lakes. This is a fine species, and 

 can be easily recognized by its thick pedicel and sessile 

 zooids. Schewiakoff ('93) marks the species with an interro- 

 gation point, but I see no reason for it. 



88. O. irritabilis Hempel ('96). 



This fine large species was found at a variety of places 

 from May to July, during which time it was common and 

 aften abundant, always occurring attached to the surface of 

 some animal, especially young musk-turtles (Aromochelys 

 odoratus). It was also found upon the backs of snapping 

 turtles (Chelydra serpentina), and on two kinds of crayfishes, 

 Cambarus diogenes and C. blandingii acutus. Its food consists 

 partly of diatoms and Euglena. 



The species is similar to Operculariq articulata Ehrbg., but 

 differs from it in the shape of the body, the character of the 

 peristome border and pharynx, and the elevation of the 

 ciliary disc. 



