HOLOTRICHA 769 



irregularly ribbon-like; five or six micronuclei; in fresh water (Faure"- 

 Fremiet and Mugard, 1946). 



D. rhabdoides F. and M. (Fig. 327, a). Cylindrical; 150-180/z by 

 40-45/z; anterior end slightly attenuated and curved, posterior end 

 rounded; the organism grows well on the gut of Chironomus larvae 

 in laboratory. 



Family 3 Pleuronematidae Kent 



Genus Pleuronema Dujardin. Ovoid to ellipsoid; peristome begins 

 at anterior end and extends for 2/3 the body length; a conspicuous 

 membrane at both edges; semicircular swelling to left near oral area; 

 no cyto pharynx; close striation longitudinal; one to many posterior 

 sensory stiff cilia; macro nucleus round or oval; a micro nucleus; a 

 contractile vacuole; trichocysts in some species; fresh or salt water, 

 also commensal in freshwater mussels. 



P. crassum D. (Fig. 327, b). 70-120/x long; somewhat compressed; 

 Woods Hole (Calkins). 



P. anodontae Kahl (Fig. 327, c). About 55m long; posterior cilium 

 about 1/2 the body length ; in Sphaerium, Anodonta. 



P. setigerum Calkins (Fig. 327, d, e). Ellipsoid; flattened; ventral 

 surface slightly concave; about 25 ciliary rows; 38-50/z long (No- 

 land) ; in salt water; Massachusetts, Florida. 



P. coronatum Kent (Fig. 327, /) . Elongate ovoid ; both ends equally 

 rounded; caudal cilia long; about 40 ciliary rows; 47-75/x long 

 (Noland, 1937) ; in fresh and salt water; Florida. 



P. marinum D. (Fig. 327, g). Elongate ovoid; trichocysts distinct; 

 caudal cilia medium long; about 50 ciliary rows; 51-126ju long 

 (Noland) ; in salt water; Florida. 



Genus Cyclidium Mtiller. Small, 15-60ju long; ovoid; usually 

 with refractile pellicle; with a caudal cilium; peristome near right 

 side; on its right edge occurs a membrane which forms a pocket 

 around cytostomal groove and on its left edge either free cilia or a 

 membrane which unites with that on right; no semicircular swelling 

 on left of oral region; round macronucleus with a micro nucleus; con- 

 tractile vacuole posterior; fresh or salt water. Numerous species. 3 

 species in sea urchin (Powers, 1935); comparison with Uronema 

 (Parducz, 1940). 



C. litomesum Stokes (Fig. 327, h). About 40m long; dorsal surface 

 slightly convex with a depression in middle; ventral surface more or 

 less concave; cilia long; in fresh water. 



Genus Cristigera Roux. Similar to Cyclidium; much compressed ; 



