598 PROTOZOOLOGY 



pools and ditches in salt marshes of California, salinities of which 

 range 3.5-10 per cent or even up to 15-20 per cent. 



*S. pharyngea Kirby (Fig. 282, d). Ovoid to ellipsoid; flattened; 84- 

 llOju by 48-65/x; gelatinous layer about 2;u thick, with bacteria; 

 about 60 longitudinal ciliary rows, each with 2 borders; peristome 

 about 35/i long, at anterior end, oblique; with closely set cilia from 

 the opposite inner surfaces; cytopharynx conspicuous; spherical 

 macro nucleus anterior, with a micro nucleus; trichocysts (7-9/i long) 

 distributed sparsely and unevenly, oblique to body surface; a group 

 of bristle-like cilia at posterior end; often brightly colored because of 

 food material; in salt marsh, California. 



S. vorax Kahl (Fig. 282, e). Broadly ellipsoid; size variable, 70- 

 180iu long; ventral surface flattened; posterior border of peristomal 

 cavity extending anteriorly; in salt marsh; California (Kirby). 



Family 7 Clathrostomidae Kahl 



Genus Clathrostoma Penard. Ellipsoid; with an oval pit in anterior 

 half of the flattened ventral surface, in which occur 3-5 concentric 

 rows of shorter cilia; cytostome a long slit located at the bottom of 

 this pit; with a basket composed of long fibrils on the outer edge of 

 the pit ; in fresh water. 



C. viminale P. (Fig. 282, /). Resembles a small Frontonia leucas; 

 macro nucleus short sausage-form; 4 micro nuclei in a compact group; 

 endoplasm with excretion crystals; 5 preoral ciliary rows; 130-180/z 

 long; in fresh water. 



Family 8 Parameciidae Grobben 



Genus Paramecium Hill {Paramaecium Miiller). Cigar- or foot- 

 shaped; circular or ellipsoid in cross section; with a single macro nu- 

 cleus and 1 to several vesicular or compact micro nuclei; peristome 

 long, broad, and slightly oblique; in fresh or brackish water. Several 

 species. 



P. caudatum Ehrenberg (Figs. 22, e; 36; 41, a-e; 50; 77; 283, a). 

 180-300/i long; with a compact micro nucleus, a massive macro nu- 

 cleus; 2 contractile vacuoles on aboral surface; posterior end bluntly 

 pointed ; in fresh water. The most widely distributed species. 



P. aurelia E. (Figs. 81; 56; 283, b). 120-180iu long; 2 small vesicu- 

 lar micro nuclei, a massive macro nucleus; 2 contractile vacuoles on 

 aboral surface; posterior end more rounded than P. caudatum; in 

 fresh water. 



P. multimicronucleatum Powers and Mitchell (Figs. 19; 20; 28; 29; 

 283, c). Slightly larger than P. caudatum; 3-7 contractile vacuoles; 4 



