EDMONDSON — PROTOZOA OF IOWA. 87 



Family, PLEURONEMID^. 



LEMBADION Perty. 



Oval when viewed dorsall}-, flattened ventrally. Peristome 

 broad and long, occupying the greater portion of the ventral sur- 

 face, with a conspicuous undulating membrane on the left border. 

 Oral aperture at the posterior end of the peristome provided with 

 a delicate membrane. A number of rigid cilia, much longer than 

 those of the general surface, projecting from the posterior border 

 of the body. 



lyEMBADiON BULLiNUM Perty. 



Having the characters of the genus. Nucleus elongated, 

 curved, in the posterior region on the left side; contractile vesicle 

 also posterior, opposite the nucleus. 



Length, 50-100 microns. (Fig. 141, PI. XIX.) 



This species, on a few occasions, has been found abundantly 

 in this state in pond water, among aquatic plants. 



Normally the movement of the organism is in a direct course, 

 but when stimulated it swims rapidly backward, rotating on its 

 longitudinal axis. Usually from foiy to six posterior setae are 

 present. 



Reproduction is by transverse division. 



CYCLIDIUM Ehrenberg. 



Oval, slightly compressed dorso-ventrally, persistent in form. 

 Oral aperture ventral, with an extensile membrane. Cilia long, 

 rigid; one or more long, hair-like setae projecting from the pos- 

 terior border. 



Cyclidium glaucoma Ehr. 



Body ovate, slightly concave on the ventral surface. Oral 

 aperture anterior to the middle of the body, with a hood-like 

 membrane. Cilia very long and rigid, arranged in longitudinal 

 rows. A single posterior seta much longer than the cilia of the 

 general surface. Nucleus central. Contractile vesicle posterior. 



Length, 20 microns. (Fig. 142, PI. XIX.) 



Cyclidium glaucoma is abundant in this state in both stagnant 

 and fresh water. Often great swarms of these animal organisms 



