EDMONDSON — PROTOZOA OF IOWA. 99 



PLEUROTRICHA Stein. 



Elongate-oval, with from five to eight frontal styles, ventral 

 styles usually arranged in two rows with a few scattered 

 additional ones, anal styles five or six, two of them near the pos- 

 terior border. Marginal setae forming a complete border. Peris- 

 tome extending about one-third the length of the body. 



Pleurotricha lanceolata Ehr. 



Body nearly three times as long as broad, wider centrally, 

 tapering toward each extremity but narrowest and somewhat 

 pointed posteriorly. Two right-hand styles arising near the pos- 

 terior border and projecting beyond it for nearly their entire 

 length. Nuclei two in number, one placed anterior to the apex 

 of the peristome. Contractile vesicle on the left side posterior to 

 the peristome. 



Length, 250 microns. (Fig. 160, PI. XXII.) 



Somewhat resembling Stylonychia but possessing no caudal setae 

 and having the anal styles arranged in two groups. 



Found in fresh water among algae but apparently not abundant 

 in this state. 



GASTROSTYLA Engelmann. 



Elongate-oval, with five or six frontal styles and usually as 

 many anal. Ventral styles in an oblique row. The series of 

 marginal setae complete. Peristome triangular, curved and pro- 

 vided with an undulating membrane. 



Gastrostyla steinii Eng. 



Body evenly rounded at each extremity. The three frontal 

 styles near the anterior border very large. Three or four scat- 

 tered ventral styles besides the oblique row. Five anal styles in 

 an oblique row not projecting beyond the posterior border. Peris- 

 tome extending about one-third the length of the body. Nuclei 

 four in number in a longitudinal row. Contractile vesicle on the 

 left side near the middle of the body. 



Length, 250 microns. (Fig. 161, PI. XXII.) 



Found in fresh water. 



OXYTRICHA Ehrenberg. 



Elongate-oval, or elliptical, very elastic. Three or more frontal 

 styles, a few scattering ventral setae and five anal styles. Peris- 



