556 



PROTOZOOLOGY 



Fig. 253. a, Pleuronema crassum, X240 (Kahl); b, P. anodontae, 

 X290 (Kahl); c, d, P. setigerum, X540 (Noland); e, P. coronatum, 

 X540 (Noland); f, P. marinum, X400 (Noland); g, Cyclidimn litome- 

 suni, X300 (Stokes); h, Cristigera phoenix, X500 (Penard); i, C. media, 

 X400 (Kahl). 



many posterior sensory bristles; macronucleus round or oval; a 

 micronucleus ; a contractile vacuole; trichocysts in some species; 

 fresh or salt water, also commensal in freshwater mussels. 



P. crassum D. (Fig. 253, a). 70-120^ long; somewhat com- 

 pressed; Woods Hole (Calkins). 



P. anodontae Kahl (Fig. 253, 6). About 55ju long; posterior 

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



P. setigerum Calkins (Fig. 253, c, d). Ellipsoid; flattened; ven- 

 tral surface slightly concave; about 25 ciUary rows; 38-50m long 

 (Noland); in salt water; Massachusetts, Florida. 



P. coronatum Kent (Fig. 253, e). Elongate ovoid; both ends 

 equally rounded; caudal setae long; about 40 ciliary rows; 47-75^ 

 long (Noland); in fresh and salt water; Florida. 



P. marinum D. (Fig. 253, /). Elongate ovoid; trichocysts dis- 

 tinct; caudal setae medium long; about 50 ciliary rows; 5 1-1 26m 

 long (Noland); in salt water; Florida. 



