EDMONDSON — PROTOZOA OF IOWA. 8 1 



broader posteriorly. Oral aperture ventral, near the anterior 

 extremity; pharynx short, curved. Nucleus spherical, central. 

 Contractile vesicle, posterior. 



Length, loo microns. (Fig. 132, PI. XVII.) 



The body of this species is more elongated and narrower than 

 Colpoda helia which it most nearly resembles. It is often found 

 in great quantities in infusions of pond water. 



Reproduction is by transverse division. 



COLPODA sp. 



Body short, reniform, wider posteriorly. Oral aperture ven- 

 tral, anterior to the center of the body. Pharynx short, slightly 

 curved. Nucleus central. Contractile vesicle posterior with 

 radiating sinuses. 



Length, 45 microns, (Fig. 133. PI. XVII.) 



Figure 133, Plate XVII, illustrates a small species which has 

 been observed with Colpoda campyla. It shows some relation to 

 Colpoda helia in the radiating sinuses of the contractile vesicle at 

 systole, but the small size would hardly permit its classification 

 with that species. 



Reproduction takes place in this minute form by transverse 

 division. 



Family, UROCENTRID^. 



UROCENTRUM Nitzsch. 



Somewhat pyriform, with an annular furrow not far from the 

 posterior extremity. Two girdles of cilia are present. Oral aper- 

 ture ventral in a longitudinal depression. A tail-like tuft of long 

 cilia arising from the ventral surface, posterior to the mouth, and 

 extending some distance beyond the posterior border of the body. 

 Nucleus and contractile vesicle in the posterior region, 



Urocentrum tubro Miill. 



Body wider and broadly rounded anteriorly, rounded or truncate 

 posteriorly. Oral aperture at the juncture of the longitudinal 

 depression and annular furrow. The posterior tuft of cilia usually 

 brush-like. Contractile vesicle posterior with the band-like nu- 

 cleus curved around it. 



Length of body, 100 microns. (Fig. 127, PI. XVI.) 



[Proc. D. a. S., Vol. XI.] ii [June i, 1906. 1 



